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 A344919 #12 Sep 07 2024 20:05:26
%S A344919 1,0,1,21,246,3110,46635,823515,16777180,387420444,9999999945,
%T A344919 285311670545,8916100448178,302875106592162,11112006825557911,
%U A344919 437893890380859255,18446744073709551480,827240261886336764024,39346408075296537575253,1978419655660313589123789,104857599999999999999999790
%N A344919 a(n) = n^n - n*(n + 1) / 2.
%F A344919 a(n) = Product_{j=1..n} n - Sum_{j=1..n} j.
%F A344919 a(n) = A000312(n) - A000217(n).
%t A344919 Join[{1},Table[n^n-(n(n+1))/2,{n,20}]] (* _Harvey P. Dale_, Sep 07 2024 *)
%o A344919 (Python)
%o A344919 def A344919(n):
%o A344919 return (n**n)-(n*(n+1)//2) # _Karl-Heinz Hofmann_, Jun 19 2021
%Y A344919 Cf. A000217, A000312, A036679, A058126.
%K A344919 nonn,easy
%O A344919 0,4
%A A344919 _Peter Luschny_, Jun 19 2021