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A187264 Number of nonempty subsets of {1, 2, ..., n} with <=3 pairwise coprime elements. 2
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 (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,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: A130972 A344483 A151923 * A067498 A018345 A082675

Adjacent sequences:  A187261 A187262 A187263 * A187265 A187266 A187267

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Mar 07 2011

STATUS

approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)