A074388 Solutions to sigma[2*(x^2)]=odd^2.

195938, 224450, 13645088, 15870978, 18180450, 29184800, 1105252128, 2363968800, 2686005218, 2917410498, 3564550178, 5056357922, 8442721568, 10814792450, 18587462432, 21292224800, 48666384162, 140836104992

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Example

m=195938=2.313.313 and sigma[195938]=294849=543.543 and 543=3.181 odd nonprime. No odd prime solutions were found below 10^12.

Mathematica

Do[s=DivisorSigma[1, 2*(n^2)]; If[IntegerQ[Sqrt[s]]&&Mod[s, 2]==1, Print[2*(n^2)]], {n, 1, 10000000}]

Crossrefs

Cf. A000203, A001248, A028982, A074386.

Sequence in context: A129486 A203047 A309190 * A234996 A234389 A234393

Adjacent sequences: A074385 A074386 A074387 * A074389 A074390 A074391

Keyword

nonn

Author

Labos Elemer, Aug 22 2002

Status

approved