User:Andrey Zabolotskiy

Андрей Заболотский, Andrei Zabolotskii.

Mathematician at the Open University, UK.

If I commented on your sequence draft, you replied, my answer is expected, but I don't answer for three days, please do not hesitate to wiki-mail me.

I write about the OEIS.

OEIS contributions, including:

• new sequences:
  • A276638, a relative of Ivan Neretin's A272727;
  • A290705, theta series of triamond (this structure actually arose in my research);
  • A348566 and A348567, related to sandpiles, also contributions to A256045, see also my Rust program that can find terms of that array and some other sequences related to sandpiles;
  • A281487 and A281488, negated sums over divisors of n (mentioned in N. J. A. Sloane's talk);
  • A293060-A293063, the crystallographic point groups, subperiodic groups, and space groups, non-magnetic and magnetic, with and without enantiomorphs. My little magnum opus;
  • A292515, related to Conway's notation for knots, together with contributions to A007022, A113204, A072552, A078666, and A078672;
  • A300782-A300784, A300651, A350871-A350872, number of distinct sublattices of various lattices, together with the major revision of the sublattices-related sequences such as A304182 and references therein, A145392, A145394, A159842, A157230, A331143;
  • A352838 and A353091, walks with given algebraic area;
  • A342811 and A342812, volume of certain permutohedra and associahedra;
  • A293237 and A293238, escape probabilities for a random walk on fcc, bcc, hcp, and diamond lattices;
  • A279903, Hausdorff dimension of E_{1,2};
  • A282137, a linear recurrence related to the Khmelnik representation of integers, A066321 (also contributions to A320283);
  • A336877 and A336878, the harmonic function on the Sierpiński gasket;
  • A336398, rational knots;
  • A279402-A279409, independence and domination numbers for toroidal chess graphs, also A321684, A342576; contributions to other chess-related graph-theoretical sequences;
  • A288535-A288537, generalization of Conway's RATS to other bases;
  • A273619, leading digit of k in base n (needed for future sequences);
  • A277054-A277059, connections between repunits and pandigitals, together with Altug Alkan (also A282429);
  • A341630, polyiamonds;
  • A332342 and A332343, continued fractions meet algebra;
  • A274137, МЩ;
  • A273975, a 3D array: expansion of ((x^k−1)/(x−1))ⁿ;
• contributions to miscellaneous nice sequences invented by other people (this list not only shows my contributions, which are often minor, but also shows what sequences I consider really nice or useful):
  • A275302-A275305, related to Langton's ant on triangular lattice, by my pupil Oleg Nikulin;
  • A275667, cellular automaton on triangular tiling, by my pupil Alexey Kovba;
  • corrections and extensions from external sources for sequences related to counting knots and links such as A002863 and A049344;
  • programs for Conway's enumeration of rational knots A122495 and links A173637 (also extension of A018240, contributions to A277740);
  • nested log formula for A278813, A278452, and related sequences;
  • a program for A277795, Equisetum-like graphs;
  • corrections and program for A267794, relative of van Eck's sequence;
  • some terms and an asymptotic formula for A277828, number of coin tosses to get a run of consecutive identical result with probability >1/2;
  • exact programs for A291259 and A123690 together with Andres Cicuttin;
  • contributions to sequences related to Lyndon words and irreducible polynomials such as A074446;
  • realizing that A132101 is a 1D analog of A250001;
  • contributions to A282390, the tripling polyominoes;
  • contribution to A089618, „a Khinchin sequence“;
  • a term for A283075, times measurable by burning ropes;
  • program for A093914, the curling number of the Thue-Morse sequence;
  • program for A287150, the fairest turn sequence for 3 players, which is in some sense a generalization of the Thue-Morse sequence;
  • a simple formula connecting A335358 and A335359, the coordinates of the points of the Koch polyline, conjectured by me and later refined and proved by my pupil Artem Litvinov;
  • illustration for A003442, rooted dissections of n-gon;
  • corrections, programs, extensions for A112410 and related sequences, carbon skeletons with rings;
  • minor corrections to sequences related to the functional equation a(a(x)) = exp(x) − 1, see A052104;
  • extension and cleanup in A164950 related to the Sprouts game;
  • contributions to A278566, related to monstrous moonshine;
  • contributions to sequences counting „chemically relevant“ graphs such as A215622 or A167227;
  • a formula for A006082, number of flat trees;
  • contributions to A296516, the number of terms in a recursively defined polynomial;
  • contributions to A228369 and A296772, the compositions of integers (see also below), also to A048793, subsets of natural numbers;
  • contribution to A001998 (I found this sequence when counted by how many ways can we stack n layers of graphene commensurately);
  • correction to A091159, nets for n-hypercube;
  • corrections and extensions from literature and databases to sequences counting lattice polytopes such as A127709, A187015, or A105232;
  • contributions to sequences counting lattices and related objects such as A097584 or A054907, see also the mention of the space groups below;
  • more terms for sequences A005368 and A259976 related to representations of some permutation groups;
  • formulas and corrections for A117966 and A244042 and a program for A059095, related to the balanced ternary representation of integers;
  • a comment for A108918, reversed binary words in reversed lexicographic order, and observations about A118319, the inverse permutation;
  • extensions from literature for sequences counting algebraic systems such as A127707 and A181769;
  • contributions to A153036, related to the Stern-Brocot tree;
  • clarifications for A085469 (also A108778), A181152, and A182566, the Madelung constants;
  • clarifications for A242674 and A246665, constants related to the secretary problem;
  • contributions to A146978, related to the Rudvalis group;
  • extension of A318271, the Bridge and Torch problem;
  • contributions to Zorach additive triangle A035312 and related sequences, including A136561;
  • contributions to A074031-A074035 and other sequences related to irreducible polynomials over GF(4);
  • investigation of A280984, guarding dominoes problem;
  • combinatorial interpretation for A302335 and A302336, related to cycles in a grid;
  • program for A189226, curvatures in an Apollonian circle packing;
  • contributions to theta series such as A217511;
  • contributions to A171108 and other sequences of Severi degrees;
  • contributions to A274369 and other Langton's ant related sequences;
  • crossrefs for A341319, related to gerrymandering;
  • collecting rows, columns and diagonals of A000027 written as a table as crossrefs for A055998;
  • identifying the „hypertriangular lattice“ from A344126 as the lcy net;
  • updates to A218537, rigid regular polygons;
  • a comment relating the triangles A099238 and A329146;
  • minor contributions to A180603 related to Brillouin zones;
  • a b-file for A039926, random digits (sic!);
  • empirical connection between a shuffling and cyclotomic polynomials, noticed in an abandoned draft and added to A289386;
  • various formulas discovered using OEIS explorer and the wonderful Sequence Machine;
  • interesting trivia: A051037 is related to bamboo, A074650 was thought to be related to DNA;
• physics:
  • I went through all sequences related to classification of n-dimensional space groups, including magnetic space groups, and contributed to some of them. This started from A006227(5), number of 5-dimensional space groups, and culminated in A293060-A293063 (see above);
  • removing heresy from A003673 and A005600, the fine-structure constant, as well as from other sequences;
  • another formula for A260832, „numbers J̃₂(n)“, which actually arose in my research;
  • contributions to A019694, 2π/5, and other sequences in connection with the redefinition of SI;
  • I went through all decimal expansions of constants of nature I could find and fixed the offsets in several of them;
  • dropping excessive digits of constants of nature;
  • references, extensions from literature, and sometimes formulas for many old sequences related to thermodynamics such as A002907, A003200, A001393, or A010571, or (surprisingly) polyominoes, such as A216820;
• preparing the list of matches between OEIS sequences and RCSR coordination sequences;
• editorial work:
  • routine, including especially reviewing, recycling, and fixing dead links;
  • making some places in the OEIS guidelines more clear and closer to the current practice;
  • killing (with keyword dead) many old incorrect sequences, merging duplicates;
  • editing of A054434, the Rubik's cube related sequence with unknown definition (I am particularly proud of solving this mystery);
  • a program and discussion of binary Barker codes A276690;
  • crossrefs between different versions of the same sequences, such as A035607 (coordination sequences for hypercubic lattices) and A066099 (compositions of integers);
  • discussion about the balance between chemical and mathematical definitions of A134818;
  • clarifications to A040004 and A287286, related to Waring's problem mod n (it took time to verify that the difference in one term only is not a mistake);
  • help with sequences from new authors such as A290772 (some cyclic Gray codes) and A292046 (related to Elias omega coding);
  • investigation of spherical curves A264759 together with main contribution from Robert Coquereaux;
  • an explanatory comment to A220952, Knuth's base-5 twisted enumeration of the nonnegative integers;
  • subtle corrections to A180620 and A231100, legs of primitive Pythagorean triples;
  • a simpler definition to A072833 (probably equivalent to the old one, no difference in the known terms);
  • fixes to PARI programs for many sequences related to binary quadratic forms;
  • comments about handling outdated content from star contributors in the discussion of A285357;
  • a comment about uninteresting conjectures in the discussion of A058077;
  • removing inappropriate unkn keyword;
  • fixing confusing names of sequences and sometimes whole obsc sequence entries: compare A162997 before and after;
  • fixing incorrect crossrefs;
  • removing email addresses of deceased contributors;
• etc.

The primary mechanism of decision-making in the OEIS community is NJAS ex machina.

Beware of the imp!