A057860 Number of residue classes modulo n which contain only composite numbers.

0, 0, 0, 1, 0, 2, 0, 3, 2, 4, 0, 6, 0, 6, 5, 7, 0, 10, 0, 10, 7, 10, 0, 14, 4, 12, 8, 14, 0, 19, 0, 15, 11, 16, 9, 22, 0, 18, 13, 22, 0, 27, 0, 22, 19, 22, 0, 30, 6, 28, 17, 26, 0, 34, 13, 30, 19, 28, 0, 41, 0, 30, 25, 31, 15, 43, 0, 34, 23

Offset

1,6

Links

G. C. Greubel, Table of n, a(n) for n = 1..10000

Formula

a(n) = n - A057859(n) = A051953(n) - A001221(n).

Example

a(30) = 19 since 30k+m is always composite if m = 0, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27 or 28

Mathematica

Table[n - EulerPhi[n] - PrimeNu[n], {n, 1, 100}] (* G. C. Greubel, May 13 2017 *)

Prog

(PARI) for(n=1, 100, print1(n - eulerphi(n) - omega(n), ", ")) \\ G. C. Greubel, May 13 2017

Crossrefs

Cf. A057858.

Sequence in context: A353335 A232343 A140944 * A092915 A063749 A231333

Adjacent sequences: A057857 A057858 A057859 * A057861 A057862 A057863

Keyword

nonn,look

Author

Henry Bottomley, Sep 08 2000

Status

approved