A015786 Numbers k such that phi(k) + 7 | sigma(k + 7).

3, 42, 162, 5478, 491910, 45504705, 175271190, 227418362790

Offset

1,1

Links

Table of n, a(n) for n=1..8.

Example

42 is a term in the sequence since phi(42) + 7 = 12 + 7 = 19 divides sigma(42 + 7) = 57.

Mathematica

Select[Range[1000000], Divisible[DivisorSigma[1, # + 7], EulerPhi[#] + 7] &] (* Amiram Eldar, Dec 10 2018 *)

Prog

(PARI) is(n)=!(sigma(n+7)%(eulerphi(n)+7)) \\ Charles R Greathouse IV, Sep 25 2012

Crossrefs

Cf. A000010, A000203.

Cf. A015775, A015781, A015782, A015783, A015784, A015785.

Sequence in context: A063040 A365594 A294517 * A229071 A220857 A340613

Adjacent sequences: A015783 A015784 A015785 * A015787 A015788 A015789

Keyword

nonn,more

Author

Robert G. Wilson v

Extensions

Corrected and a(5)-a(6) added by Charles R Greathouse IV, Sep 25 2012

a(7) from Sean A. Irvine, Dec 10 2018

a(8) from Kevin P. Thompson, Jul 23 2022

Status

approved