A050148 a(n) = T(n,n-2), array T as in A050143.

1, 7, 32, 160, 832, 4424, 23872, 130176, 715520, 3957448, 21998176, 122786976, 687736896, 3863423880, 21758302848, 122811081216, 694533774336, 3934558067336, 22323615621280, 126832567223712, 721500116473664

Offset: 2

Author

Clark Kimberling

Keywords

• nonn

Comments

Also T(2*n-2,n-2), array T as in A055807.

Crossrefs

Cf. A050143, A055807.

Formula

a(n) = Sum_{s=1..n} binomial(n,s)*binomial(s+n-4,n-3) = n*hypergeom([-n + 1, n-2], [2], -1) for n >= 3. - Petros Hadjicostas, Feb 13 2021

D-finite with recurrence (n-1)*(n-3)*a(n) +(-8*n^2+41*n-48)*a(n-1) +(13*n^2-95*n+162)*a(n-2) -2*(n-2)*(n-6)*a(n-3)=0 for n-3>=3. - R. J. Mathar, Jul 31 2025