a(n) = sqrt(sigma(2*m^2)), where m = A097023(n), i.e., sigma(2*m^2) is a square.

Terms

a(0) =543a(1) =651a(2) =5187a(3) =5973a(4) =7161a(5) =8463a(6) =57057a(7) =93093a(8) =66063a(9) =81003a(10) =80199a(11) =98553a(12) =130851a(13) =160797a(14) =216657a(15) =259749a(16) =347529a(17) =561393a(18) =565383a(19) =726693a(20) =882189a(21) =1042587a(22) =1084083a(23) =922467a(24) =1439361a(25) =1242927a(26) =1768767a(27) =1490139a(28) =2383227a(29) =2857239