A015814 Numbers k such that phi(k + 1) divides sigma(k).

1, 3, 5, 6, 7, 11, 14, 15, 17, 23, 24, 28, 31, 33, 35, 47, 51, 53, 54, 55, 69, 71, 77, 87, 94, 107, 110, 127, 155, 170, 174, 191, 195, 209, 254, 261, 265, 285, 315, 322, 383, 385, 395, 399, 406, 423, 429, 431, 510, 564, 609, 636, 644, 647, 649, 672, 713

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[1000], Divisible[DivisorSigma[1, #], EulerPhi[1 + #]] &] (* David Nacin, Mar 01 2012 *)

Prog

(PARI) is(n)=!(sigma(n)%eulerphi(n+1)) \\ Charles R Greathouse IV, Sep 25 2012

Crossrefs

Cf. A000010, A000203, A015834, A020492.

Sequence in context: A333217 A342438 A301975 * A227026 A361827 A053272

Adjacent sequences: A015811 A015812 A015813 * A015815 A015816 A015817

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Definition corrected by David Nacin, Mar 01 2012

Status

approved