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A232067 Numbers k such that sigma(k^2) and Sum_{d|k} d*sigma(d) are both multiples of k. 4
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 (list; graph; refs; listen; history; text; internal format)
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

Donovan Johnson, Table of n, a(n) for n = 1..70

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

Cf. A000203, A069520, A232354.

Sequence in context: A194133 A069520 A232354 * A247222 A268983 A293918

Adjacent sequences:  A232064 A232065 A232066 * A232068 A232069 A232070

KEYWORD

nonn

AUTHOR

M. F. Hasler, Nov 24 2013

STATUS

approved

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Last modified September 28 06:57 EDT 2021. Contains 347703 sequences. (Running on oeis4.)