A187490 Number of 3-element nondividing subsets of {1, 2, ..., n}.

1, 2, 6, 12, 22, 31, 49, 70, 99, 128, 176, 216, 284, 343, 423, 515, 633, 722, 860, 1007, 1173, 1333, 1552, 1729, 1989, 2223, 2502, 2809, 3138, 3416, 3819, 4226, 4658, 5049, 5570, 6016, 6601, 7146, 7719, 8371, 9100, 9686, 10461, 11208, 12039

Offset

7,2

Comments

A set is called nondividing if no element divides the sum of any nonempty subset of the other elements.

Links

Alois P. Heinz, Table of n, a(n) for n = 7..200

Eric Weisstein's World of Mathematics, Nondividing Set.

Example

a(7) = 1 because there is one 3-element nondividing subset of {1,2,3,4,5,6,7}: {4,6,7}.
a(9) = 6: {4,6,7}, {4,6,9}, {5,6,8}, {5,8,9}, {6,7,9}, {6,8,9}.

Crossrefs

Column 3 of triangle A187489. Cf. A068063.

Sequence in context: A062482 A046960 A126428 * A147623 A232234 A045964

Adjacent sequences: A187487 A187488 A187489 * A187491 A187492 A187493

Keyword

nonn

Author

Alois P. Heinz, Mar 10 2011

Status

approved