A187265 Number of nonempty subsets of {1, 2, ..., n} with <= 4 pairwise coprime elements.

1, 3, 7, 11, 23, 27, 53, 68, 97, 109, 193, 208, 345, 382, 437, 506, 785, 827, 1224, 1310, 1472, 1590, 2253, 2346, 2892, 3100, 3568, 3784, 5070, 5163, 6756, 7277, 7928, 8387, 9301, 9560, 12142, 12790, 13815, 14297, 17795, 18083, 22189

Offset

1,2

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Formula

a(n) = A187262(n,4).

Example

a(5) = 23 because there are 23 nonempty subsets of {1,2,3,4,5} with <=4 pairwise coprime elements: {1}, {2}, {3}, {4}, {5}, {1,2}, {1,3}, {1,4}, {1,5}, {2,3}, {2,5}, {3,4}, {3,5}, {4,5}, {1,2,3}, {1,2,5}, {1,3,4}, {1,3,5}, {1,4,5}, {2,3,5}, {3,4,5}, {1,2,3,5}, {1,3,4,5}.

Crossrefs

Column 4 of triangle A187262. First differences are A186988.

Sequence in context: A244572 A137516 A247380 * A187266 A187267 A187268

Adjacent sequences: A187262 A187263 A187264 * A187266 A187267 A187268

Keyword

nonn

Author

Alois P. Heinz, Mar 07 2011

Status

approved