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 A282510 #40 Mar 28 2017 16:28:32 %S A282510 1,2,3,1,4,5,2,3,1,3,1,4,5,2,5,2,3,1,4,6,4,5,2,3,7,8,9,1,7,8,6,4,5,9, %T A282510 10,11,2,3,1,9,10,7,8,6,11,12,13,4,5,2,3,1,8,6,9,10,7,13,14,15,11,12, %U A282510 4,5,2,3,1,10,11,12,6,9,1,7,8,13,14,15,16,4,5,2,3 %N A282510 Irregular triangle T(n,k) read by rows: Each term is the least positive integer such that no row, column, diagonal, or antidiagonal contains a repeated term; and each row terminates at k when it contains all numbers <= k. %C A282510 Similar in construction to A274651; the difference between them is that here, each row terminates at k when it contains all numbers <= k (hence this triangle is irregular, while A274651 is not). %C A282510 Conjecture: All columns and diagonals are permutations of the natural numbers; a proof will be more involved than for A274651. %C A282510 Row lengths are not (weakly) monotonically increasing: row 25 has 42 terms, row 26 has 41 terms. Row indices where row lengths decrease are: 26, 64, 144, 199, 326, 400, ... . - _Alois P. Heinz_, Mar 17 2017 %H A282510 Alois P. Heinz, <a href="/A282510/b282510.txt">Rows n = 1..160, flattened</a> %e A282510 Triangle begins: %e A282510 : 1 %e A282510 : 2 3 1 %e A282510 : 4 5 2 3 1 %e A282510 : 3 1 4 5 2 %e A282510 : 5 2 3 1 4 %e A282510 : 6 4 5 2 3 7 8 9 1 %e A282510 : 7 8 6 4 5 9 10 11 2 3 1 %e A282510 : 9 10 7 8 6 11 12 13 4 5 2 3 1 %e A282510 : 8 6 9 10 7 13 14 15 11 12 4 5 2 3 1 %e A282510 : 10 11 12 6 9 1 7 8 13 14 15 16 4 5 2 3 %e A282510 : 12 7 13 14 8 2 3 1 6 10 9 17 11 15 4 5 16 %Y A282510 Cf. A274651. %K A282510 nonn,tabf %O A282510 1,2 %A A282510 _Bob Selcoe_, Feb 19 2017