A067876 Numbers k such that sigma(k) = phi(k*bigomega(k)+1).

1, 6, 27, 30, 38, 55, 56, 85, 87, 445, 451, 476, 618, 655, 715, 717, 897, 913, 1221, 1265, 1357, 2095, 2367, 2515, 2765, 3009, 3231, 3247, 3471, 3605, 3741, 4117, 4237, 4676, 5071, 6747, 7195, 7689, 7701, 10885, 11577, 12245, 12549, 12565, 15835

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..500

Mathematica

Select[Range[16000], DivisorSigma[1, #]==EulerPhi[# PrimeOmega[#]+1]&] (* Harvey P. Dale, Dec 20 2021 *)

Prog

(PARI) is(k) = {my(f=factor(k)); sigma(f) == eulerphi(k*bigomega(f)+1); } \\ Amiram Eldar, Dec 10 2024

Crossrefs

Cf. A000010 (phi), A000203 (sigma), A001222 (bigomega).

Sequence in context: A285806 A292384 A183603 * A309337 A174226 A100784

Adjacent sequences: A067873 A067874 A067875 * A067877 A067878 A067879

Keyword

easy,nonn

Author

Benoit Cloitre, Mar 02 2002

Status

approved