This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A226238 #28 Sep 28 2023 14:21:01
%S A226238 2,12,84,780,9330,137256,2396744,48427560,1111111110,28531167060,
%T A226238 810554586204,25239592216020,854769755812154,31278135027204240,
%U A226238 1229782938247303440,51702516367896047760,2314494592664502210318,109912203092239643840220
%N A226238 a(n) = (n^n - n)/(n - 1).
%C A226238 a(n) expressed in base n is written with (n-1) ones followed by a zero. - _Michel Marcus_, Aug 25 2013
%H A226238 Michael De Vlieger, <a href="/A226238/b226238.txt">Table of n, a(n) for n = 2..387</a>
%H A226238 Tanya Khovanova and Gregory Marton, <a href="https://arxiv.org/abs/2305.10357">Archive Labeling Sequences</a>, arXiv:2305.10357 [math.HO], 2023. See p. 9.
%F A226238 a(n) = Sum_{k=1..n-1} n^k.
%F A226238 a(n) = A023037(n) - 1, for n>1. - _Michel Marcus_, Aug 25 2013
%t A226238 Array[(#^# - #)/(# - 1) &, 18, 2] (* _Michael De Vlieger_, May 24 2023 *)
%o A226238 (PARI) a(n)=(n^n-n)/(n-1)
%o A226238 (Python)
%o A226238 def A226238(n): return (n**n-n)//(n-1) # _Chai Wah Wu_, Sep 28 2023
%Y A226238 A diagonal of A228275.
%K A226238 nonn,easy
%O A226238 2,1
%A A226238 _Ralf Stephan_, Aug 25 2013