A085389 a(1) = 1; for n >= 2, a(n) = (n*(n+1)^(n-1))/(n+1).

1, 2, 12, 100, 1080, 14406, 229376, 4251528, 90000000, 2143588810, 56757583872, 1654301902188, 52644347205632, 1816448730468750, 67553994410557440, 2694045224950414864, 114692890480116793344, 5191945444217181018258, 249036800000000000000000, 12617615847934310595791220

Offset: 1

Author

Paul Barry, Jun 30 2003

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A053506, A085390.

Programs

Mathematica

A085389[n_] := If[n == 1, 1, n*(n+1)^(n-2)];
Array[A085389, 25] (* Paolo Xausa, Aug 07 2025 *)

Formula

Main subdiagonal of A085388.

a(n) = A055865(n), n>1. - R. J. Mathar, Sep 12 2008

a(n) = [x^n] x*(1 - x)/(1 - x - n*x). - Ilya Gutkovskiy, Oct 02 2017

Extensions

Name edited by Paolo Xausa, Aug 07 2025