A069058 Numbers n such that A017666(n)=phi(n).

1, 18, 72, 162, 648, 1152, 1458, 4608, 5832, 10368, 13122, 41472, 52488, 73728, 93312, 118098, 294912, 373248, 472392, 663552, 839808, 1062882, 2654208, 3359232, 4251528, 4718592, 5971968, 7558272, 9565938, 18874368, 23887872

Offset

1,2

Comments

Appears to be a subset of A195321, i.e. all terms greater than 1 are of the form 18*n^2. - William J. Keith, May 25 2016

It also appears to be a subset of A003586, i.e., all the terms below 10^12 are of the form 2^i*3^j. - Giovanni Resta, May 26 2016

Links

Giovanni Resta, Table of n, a(n) for n = 1..81 (terms < 10^12)

Mathematica

Select[Range[10^6], Denominator@ Total[1/Divisors@ #] == EulerPhi@ # &] (* Michael De Vlieger, May 25 2016 *)

Prog

(PARI) for(n=1, 2500000, if(denominator(sumdiv(n, k, 1/k)) == eulerphi(n), print1(n, ", ")))
(PARI) isok(n) = denominator(sigma(n)/n) == eulerphi(n); \\ Michel Marcus, May 26 2016

Crossrefs

Cf. A195321.

Sequence in context: A274577 A347360 A195321 * A262000 A007276 A052619

Adjacent sequences: A069055 A069056 A069057 * A069059 A069060 A069061

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 04 2002

Extensions

More terms from Rick L. Shepherd, Apr 16 2002

Status

approved