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 A368370 #20 Jan 25 2024 14:03:39
%S A368370 0,4,514,113920,44084375,28195584256,28201577788944,42039291307622400,
%T A368370 89651019067859485125,264184676314240000000000,
%U A368370 1044528435971290465713291136,5403748103160416506028643844096,35801791315095649217787108688094375
%N A368370 AGM transform of triangular numbers.
%C A368370 See A368366 for further information.
%F A368370 a(n) ~ (n*(n+1)*(n+2)/6)^n - n^n*n!*(n+1)!/2^n. - _Vaclav Kotesovec_, Jan 24 2024
%t A368370 Table[Sum[k*(k+1)/2, {k, 1, n}]^n - n^n*Product[k*(k+1)/2, {k, 1, n}], {n, 1, 12}] (* _Vaclav Kotesovec_, Jan 24 2024 *)
%o A368370 (Python)
%o A368370 from math import comb, factorial
%o A368370 def A368370(n): return comb(n+2,3)**n-(n**n*factorial(n)**2*(n+1)>>n) # _Chai Wah Wu_, Jan 25 2024
%Y A368370 Cf. A000217, A368366.
%K A368370 nonn
%O A368370 1,2
%A A368370 _N. J. A. Sloane_, Jan 24 2024