A073858 Numbers n such that sigma(phi(n)) divides phi(sigma(n)).

1, 2, 4, 9, 16, 18, 64, 100, 225, 242, 450, 516, 729, 1458, 3872, 4096, 4624, 13932, 14406, 17672, 18225, 20124, 21780, 28900, 29262, 29616, 36450, 45996, 62500, 65025, 65536, 76832, 92778, 95916, 106092, 106308, 114630, 114930

Offset

1,2

Links

Donovan Johnson, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[115000], Divisible[EulerPhi[DivisorSigma[1, #]], DivisorSigma[ 1, EulerPhi[ #]]]&] (* Harvey P. Dale, Jan 31 2021 *)

Prog

(PARI) n=0; for(m=1, 817034100, if(eulerphi(sigma(m))%sigma(eulerphi(m))==0, n++; write("b073858.txt", n " " m))) /* Donovan Johnson, Jul 05 2012 */

Crossrefs

Cf. A033632, A066930.

Sequence in context: A014290 A337343 A015730 * A006474 A110878 A253849

Adjacent sequences: A073855 A073856 A073857 * A073859 A073860 A073861

Keyword

easy,nonn

Author

Benoit Cloitre, Sep 02 2002

Status

approved