A292763 Numbers m such that sigma(m)+phi(m) == 2 mod 4.

1, 3, 5, 6, 7, 10, 11, 13, 14, 17, 19, 20, 22, 23, 26, 27, 29, 31, 34, 37, 38, 40, 41, 43, 45, 46, 47, 52, 53, 54, 58, 59, 61, 62, 67, 68, 71, 73, 74, 79, 80, 82, 83, 86, 89, 90, 94, 97, 101, 103, 104, 106, 107, 109, 113, 116, 117, 118, 122, 127, 131, 134, 136, 137, 139, 142, 146, 148, 149, 151, 153, 157

Offset: 1

Author

N. J. A. Sloane, Sep 26 2017

Keywords

• nonn

Comments

Union of {1}, A191217 and A292762.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..5000
• N. J. A. Sloane, Three (No, 8) Lovely Problems from the OEIS, Experimental Mathematics Seminar, Rutgers University, Oct 05 2017, Part I, Part 2, Slides. (Mentions this sequence)

Crossrefs

Cf. A000010, A000203.

Cf. A191217, A292762.

A065091 (odd primes) is a subsequence. - Michel Marcus, Oct 02 2017

Programs

Mathematica

Do[If[Mod[DivisorSigma[1, n] + EulerPhi[n], 4]==2, Print[n]], {n, 1, 10^3}] (* Vincenzo Librandi, Oct 02 2017 *)

PARI

isok(m) = ((sigma(m)+eulerphi(m)) % 4) == 2; \\ Michel Marcus, Oct 02 2017