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A063900 Numbers k such that sum of proper divisors or aliquot parts of k^2 (excluding 1) is a square, or A048050(k^2) is a square. 1
866, 9271, 18167, 30887, 39959, 114607, 119279, 129911, 153631, 239111, 343207, 517591, 582583, 602159, 607340, 1202282, 1397863, 1729999, 1920647, 2533183, 2547119, 2558183, 5740127, 7122959, 9379871, 10218407, 10891103, 13549399 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..100 (terms 1..55 from Harry J. Smith)
Passawan Noppakaew and Prapanpong Pongsriiam, Product of Some Polynomials and Arithmetic Functions, J. Int. Seq. (2023) Vol. 26, Art. 23.9.1.
MATHEMATICA
chowla[n_] := DivisorSigma[1, n] - n - 1; aQ[n_] := IntegerQ@Sqrt@chowla[n^2]; Select[Range[10^6], aQ] (* Amiram Eldar, Aug 30 2019 *)
PROG
(PARI) s(n)=sigma(n)-n-1;
for(n=1, 10^8, if(issquare(s(n^2)), print(n)))
(PARI) s(n)=sigma(n) - n - 1
{ n=0; for (m=1, 10^9, if(issquare(s(m^2)), write("b063900.txt", n++, " ", m); if (n==55, break)) ) } \\ Harry J. Smith, Sep 02 2009
CROSSREFS
Sequence in context: A129034 A244359 A038657 * A348818 A250522 A251060
KEYWORD
nonn
AUTHOR
Jason Earls, Aug 29 2001
EXTENSIONS
a(19)-a(28) from Harry J. Smith, Sep 02 2009
STATUS
approved

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Last modified May 23 05:54 EDT 2024. Contains 372758 sequences. (Running on oeis4.)