A034275 a(n)=f(n,n-2) where f is given in A034261.

1, 3, 14, 65, 294, 1302, 5676, 24453, 104390, 442442, 1864356, 7818538, 32657884, 135950700, 564306840, 2336457645, 9652643910, 39800950530, 163830074100, 673327275390, 2763494696820, 11327881630260, 46381659765480, 189711966348450, 775232392541724

Offset

1,2

Comments

Divisible by the Catalan numbers, by the explicit formula. - F. Chapoton, Jun 24 2021

Links

Table of n, a(n) for n=1..25.

Formula

a(n) = binomial(2*n-2,n-1)/n * (n^2-n+1).

a(n) = binomial(2*n-2,n-1) + (n-1)*binomial(2*n-2,n).

Prog

(Sage)
[binomial(2*n-2, n-1)//n * (n**2-n+1) for n in range(1, 8)]
(PARI) a(n) = binomial(2*n-2, n-1)/n * (n^2-n+1); \\ Michel Marcus, Jun 24 2021

Crossrefs

Cf. A000108, A002061, A034261, A344191, A344228.

Sequence in context: A161131 A247978 A026592 * A240008 A151322 A351068

Adjacent sequences: A034272 A034273 A034274 * A034276 A034277 A034278

Keyword

nonn,easy

Author

Clark Kimberling

Extensions

Corrected and extended by N. J. A. Sloane, Apr 21 2000

Status

approved