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A062975 Half-totient function of n is not divisible by the number of divisors of n. 0
3, 4, 6, 7, 8, 10, 11, 12, 14, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 30, 31, 32, 33, 36, 38, 42, 43, 44, 46, 47, 48, 50, 54, 56, 57, 58, 59, 60, 62, 64, 66, 67, 68, 69, 70, 71, 74, 75, 77, 78, 79, 80, 81, 83, 86, 88, 92, 93, 94, 96, 98, 100, 103, 106, 107, 108, 110, 112 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

Half-totient function is phi(n)/2 for n >= 3, A023022.

LINKS

Table of n, a(n) for n=3..71.

MATHEMATICA

Select[Range[3, 120], !Divisible[EulerPhi[#]/2, DivisorSigma[0, #]]&] (* Harvey P. Dale, Mar 08 2013 *)

PROG

(PARI) j=[]; for(n=3, 350, if(Mod(eulerphi(n)/2, numdiv(n)) !=0, j=concat(j, n))); j

CROSSREFS

Cf. A023022.

Sequence in context: A234349 A042954 A247987 * A276218 A047299 A186159

Adjacent sequences:  A062972 A062973 A062974 * A062976 A062977 A062978

KEYWORD

nonn

AUTHOR

Jason Earls, Jul 24 2001

STATUS

approved

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Last modified April 14 15:18 EDT 2021. Contains 342949 sequences. (Running on oeis4.)