A055865 Second column of triangle A055864.

0, 2, 12, 100, 1080, 14406, 229376, 4251528, 90000000, 2143588810, 56757583872, 1654301902188, 52644347205632, 1816448730468750, 67553994410557440, 2694045224950414864, 114692890480116793344, 5191945444217181018258, 249036800000000000000000, 12617615847934310595791220

Offset: 1

Author

Wolfdieter Lang Jun 20 2000

Keywords

• nonn
• easy

Links

• Paolo Xausa, Table of n, a(n) for n = 1..350
• Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

Crossrefs

Cf. A055864, A000272, A055858.

Programs

Mathematica

A055865[n_] := If[n == 1, 0, n*(n+1)^(n-2)];
Array[A055865, 25] (* Paolo Xausa, Aug 07 2025 *)

Formula

a(1) = 0; a(n) = n*(n+1)^(n-2), n >= 2.

E.g.f.: -1/2*(-W(-x)^2+x^2)/x, W(x) principal branch of Lambert's function.

a(n) = A055864(n, 2).