A171844 Row sums of triangle A171843.

1, 4, 12, 31, 77, 188, 462, 1148, 2887, 7335, 18789, 48419, 125321, 325381, 846713, 2206891, 5758797, 15040102, 39304237, 102760572, 268757551, 703079117, 1839625401, 4814107671, 12599351527, 32977310272, 86319400527, 225954695164, 591492569038, 1548419254590

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Formula

G.f.: Sum_{k>=1} x^k*(1 - x^k)/((1 - x)*(1 - 2*x + x^2 - x^k)). - Andrew Howroyd, Apr 13 2021

Example

a(4) = 31 = (1 + 3 + 6 + 21) since row 4 of triangle A171843 = (1, 3, 6, 21).

Prog

(PARI) seq(n)={Vec(sum(k=1, n, x^k*(1 - x^k)/((1 - x)*(1 - 2*x + x^2 - x^k)) + O(x*x^n)))} \\ Andrew Howroyd, Apr 13 2021

Crossrefs

Cf. A171843.

Sequence in context: A133546 A190376 A276785 * A324971 A273387 A328240

Adjacent sequences: A171841 A171842 A171843 * A171845 A171846 A171847

Keyword

nonn

Author

Gary W. Adamson, Dec 19 2009

Extensions

a(10) and a(13) corrected and a(14) and beyond from Andrew Howroyd, Apr 13 2021

Status

approved