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 A086815 #9 Jun 02 2025 00:16:20
%S A086815 0,16,1458,196608,39062500,10883911680,4069338437094,1970324836974592,
%T A086815 1200757082375992968,900000000000000000000,814027493868397611133210,
%U A086815 874465319237299285467856896,1100799962319223399900795392108
%N A086815 a(n)=(n-1)*n^(2*n).
%C A086815 (-1)*determinant of the 2n X 2n matrix M_(i,j)=j if (i+j) is multiple of n, M_(i,j)=i otherwise.
%e A086815 For n=3 the matrix is : [1 2 1 1 5 1], [1 2 2 4 2 2], [3 3 3 3 3 6], [4 2 4 4 5 4], [1 5 5 4 5 5], [6 6 3 6 6 6]
%t A086815 Table[(n-1)n^(2n),{n,20}] (* _Harvey P. Dale_, Jul 23 2013 *)
%o A086815 (PARI) a(n)=(n-1)*n^(2*n)
%Y A086815 Cf. A062206.
%K A086815 nonn
%O A086815 1,2
%A A086815 _Benoit Cloitre_, Aug 06 2003