A371785 a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(3*n-k,n-2*k).

1, 3, 14, 76, 441, 2652, 16303, 101727, 641630, 4080154, 26112384, 167978615, 1085182436, 7035477777, 45750406205, 298279844724, 1949096816505, 12761551428024, 83701819019155, 549850618355886, 3617119500327536, 23824816811652905, 157106267803712709

Offset

0,2

Links

Table of n, a(n) for n=0..22.

Formula

a(n) = [x^n] 1/((1-x+x^2) * (1-x)^(2*n)).

Prog

(PARI) a(n) = sum(k=0, n\2, (-1)^k*binomial(3*n-k, n-2*k));

Crossrefs

Cf. A024718, A371786, A371787.

Cf. A371742.

Sequence in context: A246455 A133798 A100937 * A223026 A371434 A364477

Adjacent sequences: A371782 A371783 A371784 * A371786 A371787 A371788

Keyword

nonn

Author

Seiichi Manyama, Apr 06 2024

Status

approved