A100236 Main diagonal of triangle A100235.

1, 4, 26, 139, 726, 3774, 19601, 101784, 528526, 2744419, 14250626, 73997554, 384238401, 1995189564, 10360186226, 53796120699, 279340789726, 1450500069334, 7531841136401, 39109705751344, 203080369893126

Offset: 0

Author

Paul D. Hanna, Nov 30 2004

Keywords

• nonn

Crossrefs

Cf. A100233, A100235.

Equals A087130(n) - 1.

Programs

PARI

a(n)=if(n==0,1,n*polcoeff(log((1-x)/(1-5*x-x^2)+x*O(x^n)),n))

Formula

a(n) = 5*a(n-1) + a(n-2) + 5 for n>1, with a(0)=1, a(1)=4. G.f.: Sum_{n>=1} a(n)*x^n/n = log((1-x)/(1-5*x-x^2)).