login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

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.
3

%I #13 Jul 29 2024 16:53:37

%S 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 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 1,2,4,3,6,10,5,7,14,12,9,1,2,4,3,6,8,5,15,12,14,7

%N 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 Rémy Sigrist, <a href="/A375030/b375030.txt">Table of n, a(n) for n = 1..386</a> (rows for n = 1..31 flattened)

%H Rémy Sigrist, <a href="/A375030/a375030.gp.txt">PARI program</a>.

%H Peter Luschny, <a href="/A375030/a375030.txt">Maple program</a>.

%e Triangle T(n, k) begins:

%e 1;

%e 1;

%e 1;

%e 1, 2, 4;

%e 1, 2, 4;

%e 1, 2, 6, 3;

%e 1, 2, 6, 3;

%e 1, 2, 4, 3, 6, 8;

%e 1, 2, 4, 3, 6, 8;

%e 1, 2, 4, 3, 9, 5, 10, 8;

%e 1, 2, 4, 3, 9, 5, 10, 8;

%e 1, 2, 4, 3, 6, 8, 5, 10, 12, 9;

%e 1, 2, 4, 3, 6, 8, 5, 10, 12, 9;

%e 1, 2, 4, 3, 6, 10, 5, 7, 14, 12, 9;

%e 1, 2, 4, 3, 6, 8, 5, 15, 12, 14, 7;

%e 1, 2, 4, 3, 6, 8, 5, 10, 12, 9, 7, 14, 16;

%e 1, 2, 4, 3, 6, 8, 5, 10, 12, 9, 7, 14, 16;

%e 1, 2, 4, 3, 6, 8, 5, 15, 9, 16, 14, 7, 12, 18;

%e 1, 2, 4, 3, 6, 8, 5, 15, 9, 16, 14, 7, 12, 18;

%e ...

%p # See Links section.

%o (PARI) \\ See Links section.

%Y Cf. A280864, A373797.

%K nonn,tabf

%O 1,5

%A _Rémy Sigrist_ at the suggestion of _Peter Luschny_, Jul 28 2024