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 A306728 #8 Nov 22 2023 18:05:29
%S A306728 1,4,3072,4682022912,62745927042654535680,
%T A306728 22033340103629170301586112512000000,
%U A306728 479715049773154880180722813201712394999926095872000000,1318058833735625830065875826842622254472987373414662267314001234660163584000000
%N A306728 a(n) = Product_{i=1..n, j=1..n} (i*(i+1) + j*(j+1)).
%F A306728 a(n) ~ c * 2^(n*(n+2)) * exp(Pi*n*(n+2)/2 - 3*n^2) * n^(2*n^2 - 2 - Pi/4), where c = 0.4952828896469310726828820344381813905230827930914109676983577406850360879...
%t A306728 Table[Product[i*(i+1)+j*(j+1), {i, 1, n}, {j, 1, n}], {n, 0, 8}]
%o A306728 (Python)
%o A306728 from math import prod, factorial
%o A306728 def A306728(n): return (prod(i*(i+1)+j*(j+1) for i in range(1,n) for j in range(i+1,n+1))*factorial(n))**2*(n+1)<<n # _Chai Wah Wu_, Nov 22 2023
%Y A306728 Cf. A324403, A324443.
%K A306728 nonn
%O A306728 0,2
%A A306728 _Vaclav Kotesovec_, Mar 06 2019