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A183204 Central terms of triangle A181544. 38
1, 4, 48, 760, 13840, 273504, 5703096, 123519792, 2751843600, 62659854400, 1451780950048, 34116354472512, 811208174862904, 19481055861877120, 471822589361293680, 11511531876280913760, 282665135367572129040 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The g.f. for row n of triangle A181544 is (1-x)^(3n+1)*Sum_{k>=0}C(n+k-1,k)^3*x^k.

This sequence is s_7 in Cooper's paper. - Jason Kimberley, Nov 06 2012

Diagonal of the rational function R(x,y,z,w) = 1/(1 - (w*x*y + w*x*z + w*y*z + x*y + x*z + y + z)). - Gheorghe Coserea, Jul 14 2016

This is one of the Apery-like sequences - see Cross-references. - Hugo Pfoertner, Aug 06 2017

Every prime eventually divides some term of this sequence. - Amita Malik, Aug 20 2017

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..702 (terms 0..499 from Jason Kimberley)

S. Cooper, Sporadic sequences, modular forms and new series for 1/pi, Ramanujan J., December 2012, Volume 29, Issue 1, pp 163-183.

Shaun Cooper, Jesús Guillera, Armin Straub, Wadim Zudilin, Crouching AGM, Hidden Modularity, arXiv:1604.01106 [math.NT], 5-April-2016.

Amita Malik and Armin Straub, Divisibility properties of sporadic Apéry-like numbers, Research in Number Theory, 2016, 2:5

Robert Osburn, Armin Straub, Wadim Zudilin, A modular supercongruence for 6F5: an Apéry-like story, arXiv:1701.04098 [math.NT], 2017.

Wadim Zudilin, A generating function of the squares of Legendre polynomials, preprint arXiv:1210.2493 [math.CA], 2012.

FORMULA

a(n) = [x^n] (1-x)^(3n+1) * Sum_{k>=0} C(n+k-1,k)^3*x^k.

a(n) = Sum_{j=0}^{n} C(n,j)^2 * C(2*j,n) * C(j+n,j). [Formula of Wadim Zudilin provided by Jason Kimberley, Nov 06 2012]

1/Pi = sqrt(7) Sum_{n>=0} (-1)^n a(n) (11895n + 1286)/22^(3n+3). [Cooper, equation (41)] - Jason Kimberley, Nov 06 2012

G.f.: sqrt((1-13*x+(1-26*x-27*x^2)^(1/2))/(1-21*x+8*x^2+(1-8*x)*(1-26*x-27*x^2)^(1/2)))*hypergeom([1/12,5/12],[1],13824*x^7/(1-21*x+8*x^2+(1-8*x)*(1-26*x-27*x^2)^(1/2))^3)^2. - Mark van Hoeij, May 07 2013

a(n) ~ 3^(3*n+3/2) / (4 * (Pi*n)^(3/2)). - Vaclav Kotesovec, Apr 05 2015

G.f. A(x) satisfies 1/(1+4*x)^2 * A( x/(1+4*x)^3 ) = 1/(1+2*x)^2 * A( x^2/(1+2*x)^3 ) [see Cooper, Guillera, Straub, Zudilin]. - Joerg Arndt, Apr 08 2016

a(n)=(-1)^n*binomial(3n+1,n)* 4F3({-n,n+1,n+1,n+1};{1,1,2(n+1)}; 1). - M. Lawrence Glasser, May 15 2016

Conjecture: n^3*a(n) - (2*n-1)*(13*n^2-13*n+4)*a(n-1) - 3*(n-1)*(3*n-4)*(3*n-2)*a(n-2) = 0. - R. J. Mathar, May 15 2016

0 = (-x^2+26*x^3+27*x^4)*y''' + (-3*x+117*x^2+162*x^3)*y'' + (-1+86*x+186*x^2)*y' + (4+24*x)*y, where y is g.f. - Gheorghe Coserea, Jul 14 2016

EXAMPLE

Triangle A181544 begins:

(1);

1, (4), 1;

1, 20, (48), 20, 1;

1, 54, 405, (760), 405, 54, 1;

1, 112, 1828, 8464, (13840), 8464, 1828, 112, 1; ...

MATHEMATICA

Table[Sum[Binomial[n, j]^2 * Binomial[2*j, n] * Binomial[j+n, j], {j, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Apr 05 2015 *)

PROG

(PARI) {a(n)=polcoeff((1-x)^(3*n+1)*sum(j=0, 2*n, binomial(n+j, j)^3*x^j), n)}

(MAGMA) P<x>:=PolynomialRing(Integers()); C:=Binomial;

A183204:=func<n|Coefficient((1-x)^(3*n+1)*&+[C(n+j, j)^3*x^j:j in[0..2*n]], n)>; // or directly:

A183204:=func<k|&+[C(k, j)^2*C(2*j, k)*C(j+k, j):j in[0..k]]>;

[A183204(n):n in[0..16]]; // Jason Kimberley, Oct 29 2012

CROSSREFS

Cf. A181544, A183205.

Related to diagonal of rational functions: A268545-A268555.

The Apéry-like numbers [or Apéry-like sequences, Apery-like numbers, Apery-like sequences] include A000172, A000984, A002893, A002895, A005258, A005259, A005260, A006077, A036917, A063007, A081085, A093388, A125143 (apart from signs), A143003, A143007, A143413, A143414, A143415, A143583, A183204, A214262, A219692,A226535, A227216, A227454, A229111 (apart from signs), A260667, A260832, A262177, A264541, A264542, A279619, A290575, A290576. (The term "Apery-like" is not well-defined.)

Sequence in context: A214819 A211198 A179235 * A047711 A089448 A167141

Adjacent sequences:  A183201 A183202 A183203 * A183205 A183206 A183207

KEYWORD

nonn,easy

AUTHOR

Paul D. Hanna, Dec 30 2010

STATUS

approved

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Last modified October 23 12:44 EDT 2017. Contains 293789 sequences.