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A062972 Numbers k such that the Chowla function of k is divisible by phi(k). 4
1, 2, 3, 4, 5, 7, 11, 13, 15, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

Sequence contains all primes; see A070037 for nonprime terms. - Charles R Greathouse IV, Apr 14 2010

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

MATHEMATICA

chowla[1] = 0; chowla[n_] := DivisorSigma[1, n] - n - 1; Select[Range[270], Divisible[chowla[#], EulerPhi[#]] &] (* Amiram Eldar, Dec 01 2019 *)

PROG

(PARI) j=[]; for(n=1, 600, if(Mod(sigma(n)-n-1, eulerphi(n)) == 0, j=concat(j, n))); j

CROSSREFS

Cf. A000010, A048050, A070037.

Sequence in context: A234719 A055464 A139316 * A231878 A285304 A036844

Adjacent sequences:  A062969 A062970 A062971 * A062973 A062974 A062975

KEYWORD

nonn,changed

AUTHOR

Jason Earls, Jul 24 2001

STATUS

approved

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Last modified December 6 06:34 EST 2019. Contains 329784 sequences. (Running on oeis4.)