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
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