A122920 Diagonal sums of number triangle A122919.

1, 1, 4, 12, 39, 129, 436, 1498, 5218, 18386, 65420, 234734, 848403, 3086001, 11288412, 41499354, 153247278, 568188606, 2114334312, 7893906144, 29561195238, 111007927386, 417918303144, 1577061975492, 5964172347604, 22601012748124, 85806694043116, 326343785428946, 1243200250005995

Offset

0,3

Comments

Starting with offset 1 = iterates of M * [1,1,1,0,0,0,...] where M is the tridiagonal matrix with [0,2,2,2,...] as the main diagonal and [1,1,1,...] as the super and subdiagonals. - Gary W. Adamson, Jan 09 2009

Partial sums are Fine numbers (A000957) with offset 3. - Alexander Burstein, Apr 15 2015

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Murray Tannock, Equivalence classes of mesh patterns with a dominating pattern, MSc Thesis, Reykjavik Univ., May 2016. See Appendix B2.

Formula

G.f.: ((1-x)*(1-2*x-2*x^2-sqrt(1-4*x))/(2*(2+x)*x^3)).

Conjecture: 2*n*(n+3)*a(n) - (7*n^2+9*n+4)*a(n-1) - 2*(n+1)*(2*n+1)*a(n-2) = 0. - R. J. Mathar, Nov 05 2012

a(n) ~ 2^(2*n+4) / (3*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Feb 03 2014

From Vladimir Reshetnikov, Oct 26 2015: (Start)

a(n) = 9/(16*(-2)^n) + 3*(2*n+4)!*hypergeom([1,n+5/2,n+3], [n+2,n+5], -8)/((n+1)!*(n+4)!).

a(n) = 9/(16*(-2)^n) + 8*2^n*(2*n+5)!!*hypergeom([1,n+7/2], [n+5], -8)/(n+4)! - 4*2^n*(2*n+3)!!*hypergeom([1,n+5/2], [n+4], -8)/(n+3)!. (End)

G.f. A(x) =: y satisfies 0 = (1 - x)^2 - y*(1 - 3*x + 2*x^3) + y^2*(2*x^3 + x^4). - Michael Somos, Oct 26 2015

0 = a(n)*(+16*a(n+1) - 26*a(n+2) - 98*a(n+3) + 36*a(n+4)) + a(n+1)*(+50*a(n+1) + 35*a(n+2) - 179*a(n+3) + 46*a(n+4)) + a(n+2)*(+105*a(n+2) + 47*a(n+3) - 50*a(n+4)) + a(n+3)*(+14*a(n+3) + 4*a(n+4)) for all n>=0. - Michael Somos, Oct 26 2015

Example

G.f. = 1 + x + 4*x^2 + 12*x^3 + 39*x^4 + 129*x^5 + 436*x^6 + 1498*x^7 + 5218*x^8 + ...

Mathematica

CoefficientList[Series[((1-x)*(1-2*x-2*x^2-Sqrt[1-4*x])/(2*(2+x)*x^3)), {x, 0, 20}], x] (* Vaclav Kotesovec, Feb 03 2014 *)
Table[9/(16 (-2)^n) + 3 (2n+4)! HypergeometricPFQ[{1, n+5/2, n+3}, {n+2, n+5}, -8]/((n+1)! (n+4)!), {n, 0, 20}] (* Vladimir Reshetnikov, Oct 26 2015 *)

Prog

(PARI) x='x+O('x^66); Vec(((1-x)*(1-2*x-2*x^2-sqrt(1-4*x))/(2*(2+x)*x^3))) \\ Joerg Arndt, May 08 2013

Crossrefs

Cf. A000957.

Sequence in context: A149327 A308446 A334458 * A241073 A149328 A149329

Adjacent sequences: A122917 A122918 A122919 * A122921 A122922 A122923

Keyword

easy,nonn

Author

Paul Barry, Sep 19 2006

Status

approved