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A140887 Number of nonprimes in [30n - 30, 30n] coprime to 30. 1

%I #6 Oct 04 2012 10:51:25

%S 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,

%T 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,

%U 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

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

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

%e {1,7,11,13,17,19,23,29} are coprime to 30 in [0, 30]; 1 is nonprime, so a(1) = 1.

%e {31,37,41,43,47,49,53,59} are coprime to 30 in [30, 60]; 49 is nonprime, so a(2) = 1.

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

%Y Cf. A007775.

%K nonn,easy,less

%O 1,4

%A _Juri-Stepan Gerasimov_, Jul 06 2008

%E Rewritten and extended by _Charles R Greathouse IV_, Mar 26 2010

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