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A062973 Chowla function of n is not divisible by phi(n). 0
6, 8, 9, 10, 12, 14, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Chowla's function (A048050) = sum of divisors of n except 1 and n.

LINKS

Table of n, a(n) for n=1..70.

MATHEMATICA

okcfQ[n_]:=!Divisible[DivisorSigma[1, n]-n-1, EulerPhi[n]]

Select[Range[100], okcfQ]  (* Harvey P. Dale, Feb 25 2011 *)

PROG

(PARI) j=[]; for(n=1, 400, if(Mod(sigma(n)-n-1, eulerphi(n))!=0, j=concat(j, n))); j

CROSSREFS

Sequence in context: A056653 A285847 A231879 * A070162 A030550 A048751

Adjacent sequences:  A062970 A062971 A062972 * A062974 A062975 A062976

KEYWORD

nonn

AUTHOR

Jason Earls, Jul 24 2001

STATUS

approved

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Last modified February 25 19:39 EST 2021. Contains 341618 sequences. (Running on oeis4.)