

A187263


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


2



1, 3, 6, 9, 14, 17, 24, 29, 36, 41, 52, 57, 70, 77, 86, 95, 112, 119, 138, 147, 160, 171, 194, 203, 224, 237, 256, 269, 298, 307, 338, 355, 376, 393, 418, 431, 468, 487, 512, 529, 570, 583, 626, 647, 672, 695, 742, 759, 802, 823
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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,2).


EXAMPLE

a(4) = 9 because there are 9 nonempty subsets of {1,2,3,4} with <=2 pairwise coprime elements: {1}, {2}, {3}, {4}, {1,2}, {1,3}, {1,4}, {2,3}, {3,4}.


CROSSREFS

Column 2 of triangle A187262. First differences are A039649 for n>1.
Sequence in context: A310164 A267295 A265321 * A230876 A000791 A027424
Adjacent sequences: A187260 A187261 A187262 * A187264 A187265 A187266


KEYWORD

nonn


AUTHOR

Alois P. Heinz, Mar 07 2011


STATUS

approved



