A140888 Number of nonprimes in [210n - 210, 210n] coprime to 210.

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

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*n-210, 210*n, gcd(k, 210)==1&!isprime(k))

Crossrefs

Cf. A008364, A140887.

Sequence in context: A112610 A100205 A353442 * A053753 A228380 A090068

Adjacent sequences: A140885 A140886 A140887 * A140889 A140890 A140891

Keyword

nonn,easy,less

Author

Juri-Stepan Gerasimov, Jul 06 2008

Extensions

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

Status

approved