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 A375030 #13 Jul 29 2024 16:53:37 %S A375030 1,1,1,1,2,4,1,2,4,1,2,6,3,1,2,6,3,1,2,4,3,6,8,1,2,4,3,6,8,1,2,4,3,9, %T A375030 5,10,8,1,2,4,3,9,5,10,8,1,2,4,3,6,8,5,10,12,9,1,2,4,3,6,8,5,10,12,9, %U A375030 1,2,4,3,6,10,5,7,14,12,9,1,2,4,3,6,8,5,15,12,14,7 %N A375030 Irregular triangle T(n, k), n > 0, k = 1..A373797(n), read by rows; the n-th row corresponds to the lexicographically earliest sequence S of A373797(n) distinct integers in the range 1..n such that for any prime number p, any run of consecutive multiples of p in S has length exactly 2. %H A375030 Rémy Sigrist, <a href="/A375030/b375030.txt">Table of n, a(n) for n = 1..386</a> (rows for n = 1..31 flattened) %H A375030 Rémy Sigrist, <a href="/A375030/a375030.gp.txt">PARI program</a>. %H A375030 Peter Luschny, <a href="/A375030/a375030.txt">Maple program</a>. %e A375030 Triangle T(n, k) begins: %e A375030 1; %e A375030 1; %e A375030 1; %e A375030 1, 2, 4; %e A375030 1, 2, 4; %e A375030 1, 2, 6, 3; %e A375030 1, 2, 6, 3; %e A375030 1, 2, 4, 3, 6, 8; %e A375030 1, 2, 4, 3, 6, 8; %e A375030 1, 2, 4, 3, 9, 5, 10, 8; %e A375030 1, 2, 4, 3, 9, 5, 10, 8; %e A375030 1, 2, 4, 3, 6, 8, 5, 10, 12, 9; %e A375030 1, 2, 4, 3, 6, 8, 5, 10, 12, 9; %e A375030 1, 2, 4, 3, 6, 10, 5, 7, 14, 12, 9; %e A375030 1, 2, 4, 3, 6, 8, 5, 15, 12, 14, 7; %e A375030 1, 2, 4, 3, 6, 8, 5, 10, 12, 9, 7, 14, 16; %e A375030 1, 2, 4, 3, 6, 8, 5, 10, 12, 9, 7, 14, 16; %e A375030 1, 2, 4, 3, 6, 8, 5, 15, 9, 16, 14, 7, 12, 18; %e A375030 1, 2, 4, 3, 6, 8, 5, 15, 9, 16, 14, 7, 12, 18; %e A375030 ... %p A375030 # See Links section. %o A375030 (PARI) \\ See Links section. %Y A375030 Cf. A280864, A373797. %K A375030 nonn,tabf %O A375030 1,5 %A A375030 _Rémy Sigrist_ at the suggestion of _Peter Luschny_, Jul 28 2024