Numbers k such that sigma(k^2+1) is a perfect square.

Terms

a(0) =0a(1) =13a(2) =64a(3) =67a(4) =189a(5) =344a(6) =900a(7) =2499a(8) =3028a(9) =4253a(10) =5257a(11) =6277a(12) =9075a(13) =11516a(14) =12544a(15) =18739a(16) =18925a(17) =47018a(18) =49011a(19) =62355a(20) =72981a(21) =112061a(22) =125011a(23) =125653a(24) =152765a(25) =167820a(26) =168317a(27) =174724a(28) =179040a(29) =225492