A056589 Third column sequence of unsigned triangle A056588.

1, 4, 16, 53, 166, 492, 1413, 3960, 10912, 29689, 80026, 214196, 570289, 1512300, 3998160, 10545741, 27766942, 73012060, 191785165, 503378480, 1320425536, 3462057009, 9074076786, 23776857828, 62289901081, 163159711492

Offset: 0

Author

Wolfdieter Lang Jul 10 2000

Keywords

• nonn
• easy

Crossrefs

Cf. A000045, A056588, A000012, A000071.

Formula

a(n)= -A056588(n+2, 2), n >= 0. a(n)= -2^(n+3)+F(n+4)*(F(n+3)+1), F(n)=A000045(n).

G.f.(1-x+x^2)/((1-2*x)*(1+x)*(1-3*x+x^2)*(1-x-x^2))