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 A071409 #5 Mar 30 2012 18:39:00 %S A071409 2,7,80,2692,-188160,673763328,53114341552128,11442355482580107264, %T A071409 101868843539003372580372480,-11188458083483956358422238173593600, %U A071409 39367352051951445285669984261580278202368000 %N A071409 Determinant of the n X n matrix m(i,j)=i^j+j^i. %C A071409 If n==0 mod 5 a(n) < 0 %o A071409 (PARI) for(n=1,20,print1(matdet(matrix(n,n,i,j,i^j+j^i)),",")) %K A071409 easy,sign %O A071409 1,1 %A A071409 _Benoit Cloitre_, May 28 2002