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
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 04 2002
EXTENSIONS
More terms from Rick L. Shepherd, Apr 16 2002
STATUS
approved