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A243810
Odd squares which are the sum of the divisors of some n.
2
1, 121, 961, 116281, 294849, 423801, 2989441, 7958041, 26904969, 35676729, 51279921, 71622369, 361722361, 962922961, 1891467081, 1902442689, 3255501249, 4364319969, 4755619521, 5215583961, 6431879601, 6561486009, 6835486329, 7496615889, 8666306649, 9712693809
OFFSET
1,2
COMMENTS
Odd terms of A038688, where most of the terms are even.
The corresponding values in A228061 are: 1, 11, 31, 341, 543, 651, 1729, 2821, ...
Among the known terms, the only prime powers are 121 and 961.
Next term is greater than 10^8.
LINKS
EXAMPLE
121 being an odd square and satisfying sigma(81) = 121, 121 is in the sequence.
MATHEMATICA
Select[DivisorSigma[1, Range[72000000]], OddQ[#]&&IntegerQ[Sqrt[#]]&] (* Harvey P. Dale, Aug 18 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Jun 11 2014
EXTENSIONS
a(13)-a(26) from Hiroaki Yamanouchi, Sep 27 2014
STATUS
approved