A094470 Numbers k such that phi(k) | sigma_18(k).

1, 2, 3, 6, 22, 33, 66, 262, 750, 786, 2182, 6546, 8646, 56946, 72006, 162066, 222386, 626406, 667158, 737286, 857526, 1223123, 1489686, 1782726, 2446246, 2939046, 3669369, 4388406, 4780947, 6804006, 7338738, 9561894, 10761126, 12157926

Offset

1,2

Comments

A015759 seems to be a true subsequence here.

sigma_18(n) is the sum of the 18th powers of the divisors of n (A013966). Conjecture: analogous sequences with any 4j+2 exponent instead of 18, includes all terms of A015759 [with exponent=2].

Links

Amiram Eldar, Table of n, a(n) for n = 1..130

Mathematica

Select[Range[10^6], Divisible[DivisorSigma[18, #], EulerPhi[#]] &] (* Amiram Eldar, Mar 07 2020 *)

Prog

(PARI) isok(k) = (sigma(k, 18) % eulerphi(k)) == 0; \\ Michel Marcus, Mar 07 2020

Crossrefs

Cf. A000010, A013966, A015759.

Sequence in context: A278106 A015773 A015768 * A015764 A015759 A260562

Adjacent sequences: A094467 A094468 A094469 * A094471 A094472 A094473

Keyword

nonn

Author

Labos Elemer, May 25 2004

Status

approved