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A057860 Number of residue classes modulo n which contain only composite numbers. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A208457 A232343 A140944 * A092915 A063749 A231333

Adjacent sequences:  A057857 A057858 A057859 * A057861 A057862 A057863

KEYWORD

nonn,look

AUTHOR

Henry Bottomley, Sep 08 2000

STATUS

approved

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Last modified August 1 16:12 EDT 2021. Contains 346393 sequences. (Running on oeis4.)