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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 (list; graph; refs; listen; history; text; internal format)
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

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..183

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

Cf. A000203, A038688, A228061.

Sequence in context: A203959 A211472 A223389 * A302561 A120353 A175983

Adjacent sequences:  A243807 A243808 A243809 * A243811 A243812 A243813

KEYWORD

nonn

AUTHOR

Michel Marcus, Jun 11 2014

EXTENSIONS

a(13)-a(26) from Hiroaki Yamanouchi, Sep 27 2014

STATUS

approved

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Last modified April 7 10:45 EDT 2020. Contains 333301 sequences. (Running on oeis4.)