

A140888


Number of nonprimes in [210n  210, 210n] coprime to 210.


0



6, 13, 15, 16, 18, 19, 21, 17, 21, 21, 22, 23, 18, 22, 26, 21, 22, 21, 24, 24, 22, 25, 22, 22, 26, 24, 22, 21, 28, 23, 25, 23, 25, 24, 26, 25, 22, 27, 27, 24, 27, 22, 24, 25, 23, 26, 23, 28, 23, 26, 27, 26, 27, 26, 27, 30, 22, 26, 27, 22, 25, 24, 26, 29, 27, 24, 27, 31, 25, 26
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OFFSET

1,1


COMMENTS

For almost all n, a(n) = phi(210) = 48. It first attains this value at a(1751794).


LINKS

Table of n, a(n) for n=1..70.


EXAMPLE

{1,11,13,...,209,} are coprime to 210 in [0, 210]; the nonprimes are {1,121,143,169,187,209} so a(1) = 1.


PROG

(PARI) a(n)=sum(k=210*n210, 210*n, gcd(k, 210)==1&!isprime(k))


CROSSREFS

Cf. A008364, A140887.
Sequence in context: A031113 A112610 A100205 * A053753 A228380 A090068
Adjacent sequences: A140885 A140886 A140887 * A140889 A140890 A140891


KEYWORD

nonn,easy,less


AUTHOR

JuriStepan Gerasimov, Jul 06 2008


EXTENSIONS

Corrected and rewritten by Charles R Greathouse IV, Mar 26 2010


STATUS

approved



