Numbers of the form 2*k^2 such that sigma(2*k^2) is an odd square.

Terms

a(0) =195938a(1) =224450a(2) =13645088a(3) =15870978a(4) =18180450a(5) =29184800a(6) =1105252128a(7) =2363968800a(8) =2686005218a(9) =2917410498a(10) =3564550178a(11) =5056357922a(12) =8442721568a(13) =10814792450a(14) =18587462432a(15) =21292224800a(16) =48666384162a(17) =140836104992a(18) =212352534818a(19) =217566422658a(20) =288728564418a(21) =315325993248