A187263 - OEIS

A187263

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

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

(list; graph; refs; listen; history; text; internal format)

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