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A074838 Numbers m such that sum(d|m, 1/core(d) ) is an integer where core(x) is the squarefree part of x. 1
1, 6, 8, 16, 20, 24, 54, 60, 72, 96, 126, 128, 180, 216, 243, 256, 384, 441, 486, 500, 504, 540, 648, 704, 729, 864, 891, 972, 1100, 1152, 1260, 1500, 1536, 1620, 1782, 1792, 1944, 2016, 2048, 2112, 2205, 2560, 3300, 3456, 3528, 3564, 3645, 3888, 4096 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
MATHEMATICA
f[p_, e_] := If[OddQ[e], p, 1]; sqf[n_] := Times @@ (f @@@ FactorInteger[n]); seqQ[n_] := IntegerQ @ DivisorSum[n, 1/sqf[#] &]; Select[Range[2^12], seqQ] (* Amiram Eldar, Apr 02 2020 *)
PROG
(PARI) isok(m) = denominator(sumdiv(m, d, 1/core(d))) == 1; \\ Michel Marcus, Apr 02 2020
CROSSREFS
Cf. A007913.
Sequence in context: A315934 A315935 A315936 * A315937 A315938 A315939
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Sep 09 2002
STATUS
approved

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Last modified July 22 20:28 EDT 2024. Contains 374541 sequences. (Running on oeis4.)