A108360 Expansion of (1-2x)^2/((1-x)^2(1-2x-x^2)^2).

1, 2, 5, 12, 30, 76, 194, 496, 1267, 3230, 8215, 20844, 52768, 133304, 336100, 845888, 2125381, 5332058, 13357833, 33419820, 83510018, 208437060, 519691110, 1294430448, 3221081335, 8008262966, 19893476315, 49378623564, 122473408452

Offset

0,2

Comments

Row sums of number triangle A108359.

Links

Table of n, a(n) for n=0..28.

Index entries for linear recurrences with constant coefficients, signature (6,-11,4,5,-2,-1).

Formula

G.f.: (1-4x+4x^2)/(1-6x+11x^2-4x^3-5x^4+2x^5+x^6); a(n)=sum{k=0..n, sum{j=0..n-k, C(k, j)C(n-j, k)*floor((j+2)/2)}}.

Crossrefs

Sequence in context: A026580 A092247 A331233 * A051163 A051450 A038508

Adjacent sequences: A108357 A108358 A108359 * A108361 A108362 A108363

Keyword

easy,nonn

Author

Paul Barry, May 31 2005

Status

approved