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A015837 Numbers k such that phi(k) | sigma(k + 2). 6
1, 2, 3, 4, 5, 9, 10, 12, 13, 18, 21, 22, 25, 28, 36, 38, 40, 42, 45, 52, 55, 58, 60, 90, 93, 108, 112, 117, 130, 152, 153, 156, 175, 180, 182, 187, 208, 222, 226, 228, 246, 258, 264, 280, 306, 310, 313, 380, 396, 468, 490, 504, 532, 592, 609, 628, 700, 715 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
MATHEMATICA
Select[Range[3000], Divisible[DivisorSigma[1, 2 + #], EulerPhi[#]] &] (* David Nacin, Mar 03 2012 *)
PROG
(PARI) isok(n) = !(sigma(n+2) % eulerphi(n)); \\ Michel Marcus, Feb 05 2017
CROSSREFS
Sequence in context: A361125 A081869 A246397 * A262511 A075177 A062096
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(1) = 1 inserted by Ivan Neretin, Feb 05 2017
STATUS
approved

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Last modified March 29 08:59 EDT 2024. Contains 371268 sequences. (Running on oeis4.)