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

Author

Alois P. Heinz, Mar 07 2011

Keywords

• nonn

Examples

			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}.
		

Links

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

Crossrefs

Column 4 of triangle A187262. First differences are A186988.

Formula

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