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 A286297 #14 Jun 01 2017 09:09:25 %S A286297 0,1,2,3,2,0,4,1,5,3,1,5,6,0,4,2,4,5,0,2,1,7,3,6,8,5,3,1,4,6,8,9,2,7, %T A286297 0,10,6,4,2,0,3,9,5,10,11,1,12,7,13,7,8,9,5,4,6,10,3,2,12,0,11,14,15, %U A286297 1,8,6,10,3,7,2,11,4,9,13,1,5,15,12,16,14,17 %N A286297 Irregular triangle read by rows: successive rows have lengths 1,3,5,7,..., and are filled in across rows with the smallest nonnegative number such that there is no repeat in any row, column, or diagonal of slope +-1. %C A286297 Conjecture: every column or diagonal of slope +-1 is a permutation of the nonnegative numbers. %H A286297 Alois P. Heinz, <a href="/A286297/b286297.txt">Rows n = 0..200, flattened</a> %e A286297 Triangle begins: %e A286297 ..........0, %e A286297 ........1,2,3, %e A286297 ......2,0,4,1,5, %e A286297 ....3,1,5,6,0,4,2, %e A286297 ..4,5,0,2,1,7,3,6,8, %e A286297 5,3,1,4,6,8,9,2,7,0,10, %e A286297 ... %Y A286297 Inspired by A274528, A274641, A274650. %K A286297 nonn,tabf %O A286297 0,3 %A A286297 _N. J. A. Sloane_, Jun 01 2017 %E A286297 More terms from _Alois P. Heinz_, Jun 01 2017