A097023 Numbers k such that the sum of the divisors of 2*k^2 is a square.

313, 335, 2612, 2817, 3015, 3820, 23508, 34380, 36647, 38193, 42217, 50281, 64972, 73535, 96404, 103180, 155991, 265364, 325847, 329823, 379953, 397068, 452529, 476545, 584748, 624748, 661815, 668660, 867636, 928620

Offset: 1

Author

Labos Elemer, Aug 24 2004

Keywords

• nonn

Examples

			sigma(2*313^2) = 543^2.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A000203, A008847, A074388, A097024.

Programs

Mathematica

Select[Range[950000],IntegerQ[Sqrt[DivisorSigma[1,2#^2]]]&] (* Harvey P. Dale, Jul 10 2012 *)

Formula

a(n) = sqrt(A074388(n)/2). - Amiram Eldar, Aug 13 2024

Extensions

Definition clarified by Harvey P. Dale, Jul 10 2012