A368970 Expansion of (1/x) * Series_Reversion( x * (1-x+x^3)^2 ).

1, 2, 7, 28, 121, 546, 2531, 11934, 56867, 272580, 1309505, 6285630, 30057195, 142754008, 671062828, 3108766166, 14108600499, 62170980416, 262108536781, 1027886900446, 3509371721163, 8204350476210, -12172347463045, -361684831407060, -3497893818262311

Offset

0,2

Links

Seiichi Manyama, Table of n, a(n) for n = 0..1000

Index entries for reversions of series

Formula

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

Prog

(PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x+x^3)^2)/x)
(PARI) a(n, s=3, t=2, u=0) = sum(k=0, n\s, (-1)^k*binomial(t*(n+1)+k-1, k)*binomial((t+u+1)*(n+1)-(s-1)*k-2, n-s*k))/(n+1);

Crossrefs

Cf. A063033, A368962.

Cf. A368974, A368976.

Sequence in context: A150658 A026770 A241371 * A010683 A276852 A352861

Adjacent sequences: A368967 A368968 A368969 * A368971 A368972 A368973

Keyword

sign

Author

Seiichi Manyama, Jan 10 2024

Status

approved