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A015814
Numbers k such that phi(k + 1) divides sigma(k).
1
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
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
KEYWORD
nonn
EXTENSIONS
Definition corrected by David Nacin, Mar 01 2012
STATUS
approved