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 A125599 #2 Mar 31 2012 13:20:34
%S A125599 0,1,37,4161,1010101,432988561,290738012181,282578800148737,
%T A125599 375973780484811925,657002506265664160401,1460516560427337565647925,
%U A125599 4026980002567282984447709761,13491386325240318454518243016437
%N A125599 Quotient ((2n)^(2n-2)-1)/(2n+1)/(2n-1).
%F A125599 a(n) = A125598[2n-1]/(2n+1). a(n) = (A000272[2n]-1)/(2n+1)/(2n-1). a(n) = (b^(n-1)-1)/(b-1), for b = (2n)^2.
%t A125599 Table[(((2n)^(n-1))^2-1)/(2n+1)/(2n-1),{n,1,20}]
%Y A125599 Cf. A125598 = ((n+1)^(n-1)-1)/n. Cf. A000272 = n^(n-2).
%K A125599 nonn
%O A125599 1,3
%A A125599 _Alexander Adamchuk_, Nov 26 2006