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A015819 Numbers k such that phi(k + 3) | sigma(k). 1
3, 6, 7, 11, 15, 19, 21, 23, 27, 31, 33, 42, 43, 51, 57, 59, 62, 69, 70, 71, 77, 79, 83, 84, 87, 93, 103, 131, 139, 141, 159, 163, 165, 177, 187, 189, 191, 199, 211, 213, 223, 235, 237, 251, 267, 270, 271, 282, 285, 287, 297, 311, 315, 316, 321, 330, 331 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MAPLE
select(t -> (numtheory:-sigma(t)/numtheory:-phi(t+3))::integer, [$1..1000]); # Robert Israel, Dec 13 2018
MATHEMATICA
Select[Range[1000], Divisible[DivisorSigma[1, #], EulerPhi[3 + #]] &] (* David Nacin, Mar 01 2012 *)
PROG
(PARI) is(n)=sigma(n)%(eulerphi(n+3))==0 \\ Charles R Greathouse IV, Sep 25 2012
CROSSREFS
Cf. A056097.
Contains A092109.
Sequence in context: A374845 A364927 A258233 * A298794 A181683 A084125
Adjacent sequences: A015816 A015817 A015818 * A015820 A015821 A015822
KEYWORD
nonn
AUTHOR
Robert G. Wilson v
STATUS
approved

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Last modified August 29 09:16 EDT 2024. Contains 375511 sequences. (Running on oeis4.)