A026635 Sum{T(i,j)}, 0<=i<=n, 0<=j<=n, T given by A026626.

1, 3, 8, 18, 40, 84, 174, 354, 716, 1440, 2890, 5790, 11592, 23196, 46406, 92826, 185668, 371352, 742722, 1485462, 2970944, 5941908, 11883838, 23767698, 47535420, 95070864, 190141754, 380283534, 760567096, 1521134220, 3042268470, 6084536970, 12169073972

Offset

0,2

Links

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,-1,-3,2)

Formula

G.f.: [1+x^4]/[(1-x)(1-2x)(1-x^2)]. - Ralf Stephan, Apr 30 2004

From Colin Barker, Sep 29 2017: (Start)

a(n) = (-9 + (-1)^n + 17*2^n - 6*n) / 6 for n>0.

a(n) = 3*a(n-1) - a(n-2) - 3*a(n-3) + 2*a(n-4) for n>4.

(End)

Mathematica

LinearRecurrence[{3, -1, -3, 2}, {1, 3, 8, 18, 40}, 40] (* Harvey P. Dale, Jan 17 2024 *)

Prog

(PARI) Vec((1 + x^4) / ((1 - x)^2*(1 + x)*(1 - 2*x)) + O(x^40)) \\ Colin Barker, Sep 29 2017

Crossrefs

Sequence in context: A360784 A335464 A369733 * A135094 A026657 A036384

Adjacent sequences: A026632 A026633 A026634 * A026636 A026637 A026638

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved