A023996 - OEIS

A023996

Triangle of numbers T(n,k), where T(n,k) is the number of sets S = {a_1, a_2, ..., a_k}, with 1 < a_i < a_j <= n such that no a_j divides the product of all the others.

%I #10 Jun 18 2019 03:32:04

%S 1,1,1,1,2,1,1,3,2,1,4,5,2,1,5,7,3,1,6,12,10,3,1,7,16,15,5,1,8,22,24,

%T 9,1,9,28,34,14,1,10,37,62,48,14,1,11,43,74,58,17,1,12,54,117,132,75,

%U 17,1,13,64,151,182,108,25,1,14,75,184,224,132,30,1,15,86

%N Triangle of numbers T(n,k), where T(n,k) is the number of sets S = {a_1, a_2, ..., a_k}, with 1 < a_i < a_j <= n such that no a_j divides the product of all the others.

%H Sean A. Irvine, <a href="/A023996/b023996.txt">Table of n, a(n) for n = 0..586</a> (rows 0..55 flattened)

%H Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a023/A023996.java">Java program</a> (github)

%e From _Sean A. Irvine_, Jun 17 2019: (Start)

%e 1;

%e 1, 1;

%e 1, 2, 1;

%e 1, 3, 2;

%e 1, 4, 5, 2;

%e 1, 5, 7, 3;

%e 1, 6, 12, 10, 3;

%e ... (End)

%Y Cf. A023995.

%K tabf,nonn

%O 0,5

%A Lionel Levine (levine(AT)ultranet.com)