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# User:Andrey Zabolotskiy

### From OeisWiki

Theoretical physicist, MSc in applied physics and mathematics (MIPT, 2014)

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.

OEIS contributions, including:

- miscellaneous new sequences:
- A276638, a relative of Ivan Neretin's A272727;
- A290705, theta series of triamond (this structure actually arose in my research);
- A281487 and A281488, negated sums over divisors of
*n*(mentioned in N. J. A. Sloane's talk); - 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);

- new sequences partly taken from published sources:
- 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, A072552, A078666, and A078672;
- 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;
- A279402-A279409, independence and domination numbers for toroidal chess graphs; also, corrections to A274947 and hence A250000, squares attacked by queens;
- A288535-A288537, generalization of Conway's RATS to other bases;
- 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):
- programs for Conway's enumeration of rational knots A122495 and links A173637;
- 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;
- 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;
- contribution to A228369, the compositions of integers;
- contribution to A001998 (I found this sequence when counted by how many ways can we stack n layers of graphene commensurately);
- contributions to Zorach additive triangle A035312 and related sequences, including A136561;

- cellular automata:
- physics:
- I went through all sequences related to classification of n-dimensional 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;
- another formula for A260832, "numbers
*J̃*_{2}(*n*)", which actually arose in my research; - I went through all decimal expansions of constants of nature I could find and fixed the offsets in several of them;
- references and sometimes formulas for some old physics-related sequences;

- editorial work:
- routine;
- killing (with keyword
`dead`) many old incorrect sequences; - editing of A054434, the Rubick'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 A035607 (it turned out that there are 5 versions of the same array, mostly not cross-referenced);
- 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 A290772 (some cyclic Gray codes) and A292046 (related to Elias omega coding);
- fixing old
`obsc`sequences: compare A162997 before and after;

- etc.

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