A369266 Expansion of (1/x) * Series_Reversion( x * (1-x) / (1+x^3)^2 ).

1, 1, 2, 7, 24, 84, 313, 1209, 4769, 19166, 78253, 323570, 1352122, 5701467, 24229122, 103663575, 446163435, 1930390329, 8391341664, 36630504952, 160509484616, 705750073063, 3112865367660, 13769327908980, 61066953746400, 271488240652950, 1209671359828154

Offset

0,3

Links

Table of n, a(n) for n=0..26.

P. Bala, Fractional iteration of a series inversion operator

Index entries for reversions of series

Formula

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

a(n) = (1/(n+1)) * [x^n] ( 1/(1-x) * (1+x^3)^2 )^(n+1). - Seiichi Manyama, Feb 14 2024

Prog

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

Crossrefs

Cf. A071969, A369268.

Cf. A369267, A370248.

Sequence in context: A370477 A088854 A000777 * A144170 A369296 A297345

Adjacent sequences: A369263 A369264 A369265 * A369267 A369268 A369269

Keyword

nonn

Author

Seiichi Manyama, Jan 18 2024

Status

approved