A054133 T(2n-1,n) where T is the array in A054126.

2, 7, 39, 236, 1479, 9418, 60492, 390720, 2534115, 16489802, 107594725, 703681448, 4611414244, 30273029080, 199045400424

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• more

Crossrefs

Cf. A054126.

Programs

PARI

a(n) = if(n==1, 2, 2^(n-2) + sum(m=0, n-1, binomial(3*n-1, m))) \\ Jianing Song, May 30 2022

Formula

a(n) = A052509(4*n-2,3*n) + A052509(4*n-2,n-1) = 2^(n-2) + Sum_{m=0..n-1} binomial(3*n-1,m) for n >= 2. - Jianing Song, May 30 2022

Extensions

Definition clarified by Eric Rowland, May 29 2022