A062975 Half-totient function of n is not divisible by the number of divisors of n.

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

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: A042954 A361457 A247987 * A276218 A047299 A186159

Adjacent sequences: A062972 A062973 A062974 * A062976 A062977 A062978

Keyword

nonn

Author

Jason Earls, Jul 24 2001

Status

approved