A371854 a(n) = Sum_{k=0..floor(n/3)} binomial(2*n-k+2,n-3*k).

1, 4, 15, 57, 219, 847, 3290, 12819, 50066, 195909, 767790, 3013002, 11837043, 46548919, 183209125, 721628692, 2844297119, 11217639757, 44265835891, 174765349896, 690308413773, 2727823240762, 10783518961394, 42644560775835, 168699835910561, 667580653569309

Offset

0,2

Links

Table of n, a(n) for n=0..25.

Formula

a(n) = [x^n] 1/(((1-x)^2-x^3) * (1-x)^(n+1)).

Prog

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

Crossrefs

Cf. A002450, A105872, A371842.

Cf. A360150, A371773.

Sequence in context: A125145 A242781 A346195 * A277924 A371777 A095930

Adjacent sequences: A371851 A371852 A371853 * A371855 A371856 A371857

Keyword

nonn

Author

Seiichi Manyama, Apr 09 2024

Status

approved