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A232067
Numbers k such that sigma(k^2) and Sum_{d|k} d*sigma(d) are both multiples of k.
3
1, 39, 793, 2379, 7137, 76921, 230763, 692289, 2076867, 8329831, 24989493, 53695813, 74968479, 161087439, 224905437, 243762649, 324863409, 375870691, 483262317, 731287947, 1127612073, 1449786951, 2094136707, 2193863841, 2631094837, 3382836219, 3606816823
OFFSET
1,2
COMMENTS
Intersection of A069520 and A232354.
Can these numbers be characterized as the terms of A232354 which do not have a factor in {11, 1093, ...}? Is this A090814, or (a subsequence of) A126197?
LINKS
MATHEMATICA
fQ[n_] := Mod[DivisorSigma[1, n^2], n] == 0 && Mod[DivisorSum[n, #*DivisorSigma[1, #] &], n] == 0; Select[Range[100000], fQ] (* T. D. Noe, Nov 25 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Nov 24 2013
STATUS
approved