A187264 - OEIS

A187264

Number of nonempty subsets of {1, 2, ..., n} with <=3 pairwise coprime elements.

1, 3, 7, 11, 21, 25, 43, 54, 73, 83, 125, 136, 194, 215, 245, 278, 374, 396, 516, 552, 614, 662, 834, 871, 1018, 1087, 1215, 1285, 1555, 1592, 1900, 2023, 2181, 2298, 2506, 2581, 3013, 3160, 3378, 3497, 4027, 4105, 4689, 4875, 5103

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OFFSET

1,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A187262(n,3).

EXAMPLE

a(4) = 11 because there are 11 nonempty subsets of {1,2,3,4} with <=3 pairwise coprime elements: {1}, {2}, {3}, {4}, {1,2}, {1,3}, {1,4}, {2,3}, {3,4}, {1,2,3}, {1,3,4}.

CROSSREFS

Column 3 of triangle A187262. First differences are A186987.

Sequence in context: A350400 A344483 A151923 * A067498 A018345 A082675

Adjacent sequences: A187261 A187262 A187263 * A187265 A187266 A187267

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Mar 07 2011

STATUS

approved