

A248727


A046802(x,y) > A046802(x,y+1), transform of e.g.f. for the graded number of positroids of the totally nonnegative Grassmannians G+(k,n); enumerates faces of the stellahedra.


7



1, 2, 1, 5, 5, 1, 16, 24, 10, 1, 65, 130, 84, 19, 1, 326, 815, 720, 265, 36, 1, 1957, 5871, 6605, 3425, 803, 69, 1, 13700, 47950, 65646, 44240, 15106, 2394, 134, 1, 109601, 438404, 707840, 589106, 267134, 63896, 7094, 263, 1
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OFFSET

0,2


COMMENTS

This is a transform of A046802 treating it as an array of hvectors, so y is replaced by (y+1) in the e.g.f. for A046802.
An e.g.f. for the reversed row polynomials with signs is given by exp(a.(0;t)x) = [e^{(1+t)x} [1+t(1e^(x))]]^(1) = 1  (1+2t)x + (1+5t+5t^2)x^2/2! + ... . The reciprocal is an e.g.f. for the reversed face polynomials of the simplices A074909, i.e., exp(b.(0;t)x) = e^{(1+t)x} [1+t(1e^(x))] = 1 + (1+2t)x +(1+3t+3t^2) x^2/2! + ... , so the relations of A133314 apply between the two sets of polynomials. In particular, umbrally [a.(0;t)+b.(0;t)]^n vanishes except for n=0 for which it's unity, implying the two sets of Appell polynomials formed from the two bases, a_n(z;t) = (a.(0;t)+z)^n and b_n(z;t) = (b.(0;t) + z)^n, are an umbral compositional inverse pair, i.e., b_n(a.(x;t);t)= x^n = a_n(b.(x;t);t). Raising operators for these Appell polynomials are related to the polynomials of A028246, whose reverse polynomials are given by A123125 * A007318. Compare: A248727 = A007318 * A123125 * A007318 and A046802 = A007318 * A123125. See A074909 for definitions and related links.  Tom Copeland, Jan 21 2015
The o.g.f. for the umbral inverses is Og(x) = x / (1  x b.(0;t)) = x / [(1tx)(1(1+t)x)] = x + (1+2t) x^2 + (1+3t+3t^2) x^3 + ... . Its compositional inverse is an o.g.f for signed A033282, the reverse fpolynomials for the simplicial duals of the Stasheff polytopes, or associahedra of type A, Oginv(x) =[1+(1+2t)xsqrt[1+2(1+2t)x+x^2]] / (2t(1+t)x) = x  (1+2t) x^2 + (1+5t+5t^2) x^3 + ... . Contrast this with the o.g.f.s related to the corresponding hpolynomials in A046802.  Tom Copeland, Jan 24 2015
Face vectors, or coefficients of the face polynomials, of the stellahedra, or stellohedra. See p. 59 of Buchstaber and Panov.  Tom Copeland, Nov 08 2016
See A008279 for a relation between the e.g.f.s enumerating the faces of permutahedra and stellahedra.  Tom Copeland, Nov 14 2016


LINKS

Table of n, a(n) for n=0..44.
P. Barry, Three Études on a sequence transformation pipeline, arXiv:1803.06408 [math.CO], 2018.
L. Berry, S. Forcey, M. Ronco, and P. Showers, Polytopes and Hopf algebras of painted trees: Fan graphs and Stellohedra, arXiv:1608.08546 [math.CO], 2018.
V. Buchstaber and T. Panov, Toric Topology, arXiv:1210.2368v3 [math.AT], 2014.
R. Da Rosa, D. Jensen, and D. Ranganathan, Toric graph associahedra and compactifications of M_(0,n), arXiv:1411.0537 [math.AG], 2015.
S. Forcey, M. Ronco, and P. Showers, Polytopes and algebras of grafted trees: Stellohedra, arXiv:1608.08546v2 [math.CO], 2016.
Stefan Forcey, The Hedra Zoo
I. Limonchenko, Momentangle manifolds, 2truncated cubes and Massey operations, arXiv:1510.07778 [math.AT], 2017.
M. Lin, Graph Cohomology, 2016, (Fig. 2.5 is a stellahedron).
T. Manneville and V. Pilaud, Compatability fans for graphical nested complexes, arXiv:1501.07152v3 [math.CO], 20152016.
V. Pilaud, The Associahedron and its Friends, presentation for Seminaire Lotharingien de Combinatoire, April 46, 2016. [From Tom Copeland, Jun 26 2018]


FORMULA

Let M(n,k)= sum{i=0,..,k1, C(n,i)[(ik)^i*(ki+1)^(ni) (ik+1)^i*(ki)^(ni)]} with M(n,0)=1. Then M(n,k)= A046802(n,k), and T(n,j)= sum(k=j,..,n, C(k,j)*M(n,k)) for j>0 with T(n,0)= 1 + sum(k=1,..,n, M(n,k)) for n>0 and T(0,0)=1.
E.g.f: y * exp[x*(y+1)]/[y+1exp(x*y)].
Row sums are A007047. Row polynomials evaluated at 1 are unity. Row polynomials evaluated at 2 are A122045.
First column is A000522. Second column appears to be A036918/2 = (A0013391)/2 = n*A000522(n)/2.
Second diagonal is A052944. (Changed from conjecture to fact on Nov 08 2016.)
The raising operator for the reverse row polynomials with row signs is R = x  (1+t)  t e^(D) / [1 + t(1e^(D))] evaluated at x = 0, with D = d/dx. Also R = x  d/dD log[exp(a.(0;t)D], or R =  d/dz log[e^(xz) exp(a.(0;t)z)] =  d/dz log[exp(a.(x;t)z)] with the e.g.f. defined in the comments and z replaced by D. Note that t e ^(D) / [1+t(1e^(D))] = t  (t+t^2) D + (t+3t^2+2t^3) D^2/2!  ... is an e.g.f. for the signed reverse row polynomials of A028246.  Tom Copeland, Jan 23 2015
Equals A007318*(padded A090582)*A007318*A097808 = A007318*(padded (A008292*A007318))*A007318*A097808 = A007318*A130850 = A007318*(mirror of A028246). Padded means in the same way that A097805 is padded A007318.  Tom Copeland, Nov 14 2016
Umbrally, the row polynomials are p_n(x) = (1 + q.(x))^n, where (q.(x))^k = q_k(x) are the row polynomials of A130850.  Tom Copeland, Nov 16 2016
From the previous umbral statement, OP(x,d/dy) y^n = (y + q.(x))^n, where OP(x,y) = exp[y * q.(x)] = x/((1+x)*exp(x*y)  1), the e.g.f. of A130850, so OP(x,d/dy) y^n evaluated at y = 1 is p_n(x), the nth row polynomial of this entry, with offset 0.  Tom Copeland, Jun 25 2018


MAPLE

The triangle T(n, k) starts:
n\k 0 1 2 3 4 5 6 7 ...
1: 1
2: 2 1
3: 5 5 1
4: 16 24 10 1
5: 65 130 84 19 1
6: 326 815 720 265 36 1
7: 1957 5871 6605 3425 803 69 1
8: 13700 47950 65646 44240 15106 2394 134 1
... reformatted, Wolfdieter Lang, Mar 27 2015


MATHEMATICA

(* t = A046802 *) t[_, 1] = 1; t[n_, n_] = 1; t[n_, 2] = 2^(n  1)  1; t[n_, k_] = Sum[((i  k + 1)^i*(k  i)^(n  i  1)  (i  k + 2)^i*(k  i  1)^(n  i  1))*Binomial[n  1, i], {i, 0, k  1}]; T[n_, j_] := Sum[Binomial[k, j]*t[n + 1, k + 1], {k, j, n}]; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* JeanFrançois Alcover, Jan 23 2015, after Tom Copeland *)


CROSSREFS

Cf. A046802, A007047, A122045, A000522, A036918, A001339, A052944.
Cf. A074909, A028246, A133314, A007318, A123125, A033282.
Cf. A008279, A008292, A090582, A097808, A130850.
Sequence in context: A124733 A137597 A059340 * A270250 A204119 A046757
Adjacent sequences: A248724 A248725 A248726 * A248728 A248729 A248730


KEYWORD

easy,nonn,tabl


AUTHOR

Tom Copeland, Oct 12 2014


EXTENSIONS

Title expanded by Tom Copeland, Nov 08 2016


STATUS

approved



