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A069236 Integers m, not a perfect square, such that the squarefree part of m divides phi(m). 1
8, 18, 27, 32, 50, 54, 72, 98, 108, 125, 128, 147, 162, 200, 216, 242, 243, 250, 288, 294, 338, 343, 392, 432, 450, 486, 500, 507, 512, 578, 588, 605, 648, 675, 686, 722, 800, 864, 882, 968, 972, 1000, 1014, 1029, 1058, 1083, 1125, 1152, 1176, 1210, 1250 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
108 is not a square, phi(108)=36, 3 is the squarefree part of 108 and 3 divides 36. Hence a(9)=108 is in the sequence.
MATHEMATICA
f[p_, e_] := (p - 1)*p^((e - 1) - Mod[e, 2]); q[n_] := ! AllTrue[(fct = FactorInteger[n])[[;; , 2]], EvenQ] && IntegerQ[Times @@ f @@@ fct]; Select[Range[2, 1250], q] (* Amiram Eldar, Mar 09 2021 *)
PROG
(PARI) isok(m) = !issquare(m) && !(eulerphi(m) % core(m)); \\ Michel Marcus, Nov 30 2020
CROSSREFS
Sequence in context: A298161 A195419 A110188 * A187101 A051370 A290614
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 13 2002
EXTENSIONS
Name edited by Michel Marcus, Nov 30 2020
STATUS
approved

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Last modified April 20 21:11 EDT 2024. Contains 371845 sequences. (Running on oeis4.)