A119655 a(0) = a(1) = 0. a(n) = number of earlier terms of the sequence which are not coprime to n.

0, 0, 2, 2, 4, 2, 6, 2, 8, 3, 9, 2, 12, 2, 12, 7, 13, 2, 16, 2, 16, 8, 18, 2, 22, 2, 23, 8, 24, 2, 27, 2, 26, 11, 27, 3, 32, 2, 29, 14, 30, 2, 38, 2, 35, 14, 36, 2, 42, 7, 39, 16, 41, 2, 46, 6, 45, 19, 43, 2, 51, 2, 44, 24, 46, 8, 57, 2, 50, 24, 55, 2, 61, 2, 53, 25, 55, 13, 64, 2, 60

Offset

0,3

Links

Diana L. Mecum, Table of n, a(n) for n = 0..1199

Example

Among the first 20 terms of the sequence there are 8 terms which are not coprime to 21 - a(0)=0, a(1)=0, a(6)=6, a(9)=3, a(10)=9, a(12)=12, a(14)=12 and a(15)=7. So a(21) = 8.

Mathematica

a = {0, 0}; Do[AppendTo[a, Length[Select[a, GCD[Length[a], # ] > 1 &]]], {70}]; a (* Stefan Steinerberger, Oct 16 2007 *)

Crossrefs

Sequence in context: A118982 A129457 A275365 * A364949 A083260 A284011

Adjacent sequences: A119652 A119653 A119654 * A119656 A119657 A119658

Keyword

nonn

Author

Leroy Quet, Jul 28 2006

Extensions

More terms from Stefan Steinerberger, Oct 16 2007

More terms from Diana L. Mecum, Aug 15 2008

Status

approved