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A015733
Numbers k such that d(k) does not divide phi(k).
8
2, 4, 6, 12, 14, 16, 20, 22, 25, 27, 32, 36, 38, 42, 44, 46, 48, 50, 54, 60, 62, 64, 66, 68, 75, 80, 81, 86, 92, 94, 96, 100, 112, 114, 116, 118, 121, 132, 134, 138, 142, 144, 150, 154, 158, 160, 162, 164, 166, 180, 186, 188, 189, 192, 196, 200, 204
OFFSET
1,1
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..18157 (first 2000 terms from Enrique PĂ©rez Herrero)
MATHEMATICA
Select[Range[204], ! Divisible[EulerPhi[#], DivisorSigma[0, #]] &]
PROG
(PARI) is(k) = {my(f = factor(k), d = numdiv(f), p = eulerphi(f)); p % d; } \\ Amiram Eldar, May 15 2024
CROSSREFS
Cf. A000005 (d), A000010 (phi), A015734, A020491 (d(k) does divide phi(k)).
Sequence in context: A056371 A271822 A067874 * A247460 A023187 A061012
KEYWORD
nonn
STATUS
approved