A226238 a(n) = (n^n - n)/(n - 1).

2, 12, 84, 780, 9330, 137256, 2396744, 48427560, 1111111110, 28531167060, 810554586204, 25239592216020, 854769755812154, 31278135027204240, 1229782938247303440, 51702516367896047760, 2314494592664502210318, 109912203092239643840220

Offset: 2

Author

Ralf Stephan, Aug 25 2013

Keywords

• nonn
• easy

Comments

a(n) expressed in base n is written with (n-1) ones followed by a zero. - Michel Marcus, Aug 25 2013

Links

• Michael De Vlieger, Table of n, a(n) for n = 2..387
• Tanya Khovanova and Gregory Marton, Archive Labeling Sequences, arXiv:2305.10357 [math.HO], 2023. See p. 9.

Crossrefs

A diagonal of A228275.

Programs

Mathematica

Array[(#^# - #)/(# - 1) &, 18, 2] (* Michael De Vlieger, May 24 2023 *)

PARI

a(n)=(n^n-n)/(n-1)

Python

def A226238(n): return (n**n-n)//(n-1) # Chai Wah Wu, Sep 28 2023

Formula

a(n) = Sum_{k=1..n-1} n^k.

a(n) = A023037(n) - 1, for n>1. - Michel Marcus, Aug 25 2013