A062976 Half-totient function of n is divisible by the number of divisors of n.

5, 9, 13, 15, 17, 28, 29, 34, 35, 37, 39, 40, 41, 45, 49, 51, 52, 53, 55, 61, 63, 65, 72, 73, 76, 82, 84, 85, 87, 89, 90, 91, 95, 97, 99, 101, 102, 104, 105, 109, 111, 113, 115, 117, 119, 120, 123, 124, 128, 130, 136, 137, 140, 143, 145, 146, 147, 148, 149, 153, 155

Offset

3,1

Comments

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

Links

Table of n, a(n) for n=3..63.

Mathematica

Select[Range[200], Divisible[EulerPhi[#]/2, DivisorSigma[0, #]]&] (* Harvey P. Dale, Feb 06 2019 *)

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: A314651 A194371 A314652 * A354798 A314653 A080580

Adjacent sequences: A062973 A062974 A062975 * A062977 A062978 A062979

Keyword

nonn

Author

Jason Earls, Jul 24 2001

Status

approved