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A069185
Numbers n such that n=phi(n)*core(n) where phi(x) is the Euler totient function and core(x) the squarefree part of x (the smallest integer such that x*core(x) is a square).
1
1, 2, 8, 12, 32, 48, 108, 128, 192, 432, 512, 768, 972, 1728, 2048, 3072, 3888, 6912, 8192, 8748, 12288, 15552, 27648, 32768, 34992, 49152, 62208, 78732, 110592, 131072, 139968, 196608, 248832, 314928, 442368, 524288, 559872, 708588, 786432, 995328, 1259712
OFFSET
1,2
LINKS
FORMULA
{1} union {numbers of form 2^(2u+1)} union {numbers of form 4^(u+1)*3^(2v+1)} u, v>=0. - Benoit Cloitre, Aug 31 2004
MATHEMATICA
f[p_, e_] := (p^e - p^(e - 1)) * p^Mod[e, 2]; aQ[1] = True; aQ[n_] := Times @@ (f @@@ FactorInteger[n]) == n; Select[Range[10000], aQ] (* Amiram Eldar, Aug 05 2019 *)
CROSSREFS
Sequence in context: A048074 A126775 A306898 * A037197 A125712 A062290
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 14 2002
EXTENSIONS
More terms from Amiram Eldar, Aug 05 2019
STATUS
approved