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 A113456 #7 Jan 27 2019 21:26:39 %S A113456 1,2,1,33,3,1,19940,3,2,1,204323,213,155,3,1,380480345,213,7572,3,2,1 %N A113456 Square array read by antidiagonals: a(n, d) is the smallest number that begins an arithmetic progression with common difference d of n numbers with the same prime signature. %C A113456 First two columns are A034173 and A113457. First three rows are A000012, A086489 and A113458. %e A113456 a(3, 2) = 3 because 3, 5 and 7 have the same prime signature. %K A113456 nonn,tabl,less %O A113456 1,2 %A A113456 _David Wasserman_, Jan 08 2006; corrected Jan 08 2006