A066995 Numbers k such that sigma(k) divides k*phi(k).

1, 6, 15, 28, 84, 95, 140, 182, 190, 248, 270, 287, 308, 357, 420, 455, 477, 496, 570, 672, 744, 819, 840, 910, 1199, 1428, 1488, 1547, 1638, 1722, 1848, 1892, 2295, 2398, 2480, 2660, 2730, 3339, 3417, 3472, 3515, 3596, 3640, 3720, 3780, 3956, 4064, 4095

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[4500], Divisible[# EulerPhi[#], DivisorSigma[1, #]]&]  (* Harvey P. Dale, Mar 19 2011 *)

Prog

(PARI) { n=0; for (m=1, 10^10, if ((m*eulerphi(m)) % sigma(m) == 0 , write("b066995.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Apr 24 2010
(PARI) isok(n) = frac(n*eulerphi(n)/sigma(n)) == 0; \\ Michel Marcus, Jan 31 2018
(GAP) Filtered([1..10^5], n ->  n*Phi(n) mod Sigma(n) = 0); # Muniru A Asiru, Jan 31 2018

Crossrefs

Cf. A001599, A011775.

Sequence in context: A026102 A338024 A144519 * A263896 A295979 A338488

Adjacent sequences: A066992 A066993 A066994 * A066996 A066997 A066998

Keyword

nonn

Author

Benoit Cloitre, Jan 27 2002

Status

approved