A140887 Number of nonprimes in [30n - 30, 30n] coprime to 30.

1, 1, 1, 2, 3, 2, 3, 2, 3, 3, 4, 2, 3, 4, 2, 3, 3, 6, 3, 3, 3, 2, 4, 4, 4, 3, 5, 2, 4, 4, 4, 4, 4, 3, 3, 4, 2, 5, 5, 4, 3, 4, 4, 2, 6, 5, 5, 3, 4, 1, 6, 3, 4, 2, 5, 4, 4, 5, 4, 4, 5, 6, 1, 5, 5, 5, 3, 3, 5, 3, 5, 3, 6, 5, 4, 4, 3, 5, 4, 1, 5, 4, 5, 7, 3, 5, 5, 5, 4, 1, 3, 4, 5, 3, 5, 4, 4, 5, 4, 6, 4, 5, 3, 6, 6

Offset: 1

Author

Juri-Stepan Gerasimov, Jul 06 2008

Keywords

• nonn
• easy
• less

Comments

For almost all n, a(n) = phi(30) = 8. It first attains this value at a(361).

Examples

			{1,7,11,13,17,19,23,29} are coprime to 30 in [0, 30]; 1 is nonprime, so a(1) = 1.
{31,37,41,43,47,49,53,59} are coprime to 30 in [30, 60]; 49 is nonprime, so a(2) = 1.
		

Crossrefs

Cf. A007775.

Programs

Mathematica

Table[Count[Range[30n-30,30n],?(CoprimeQ[#,30]&&!PrimeQ[#]&)],{n,110}] (* _Harvey P. Dale, Oct 04 2012 *)

Extensions

Rewritten and extended by Charles R Greathouse IV, Mar 26 2010