A383355 Expansion of 1/sqrt( (1-x) * (1-x-4*x^4) ).

1, 1, 1, 1, 3, 5, 7, 9, 17, 31, 51, 77, 129, 227, 391, 641, 1067, 1829, 3157, 5351, 9033, 15399, 26471, 45349, 77387, 132293, 227153, 390379, 670013, 1149819, 1976595, 3402137, 5856157, 10079327, 17358491, 29918957, 51590271, 88971985, 153484661, 264898703, 457374335

Offset

0,5

Links

Table of n, a(n) for n=0..40.

Formula

a(n) = Sum_{k=0..floor(n/4)} binomial(2*k,k) * binomial(n-3*k,k).

Prog

(PARI) a(n) = sum(k=0, n\4, binomial(2*k, k)*binomial(n-3*k, k));

Crossrefs

Cf. A026569, A217615.

Cf. A360310.

Sequence in context: A191356 A144753 A220221 * A212292 A270837 A057482

Adjacent sequences: A383352 A383353 A383354 * A383356 A383357 A383358

Keyword

nonn

Author

Seiichi Manyama, May 01 2025

Status

approved