Numbers k such that sigma_2(k^2 + 1) == 0 (mod k).

Terms

a(0) =1a(1) =2a(2) =5a(3) =7a(4) =13a(5) =25a(6) =34a(7) =52a(8) =89a(9) =93a(10) =100a(11) =200a(12) =233a(13) =338a(14) =610a(15) =850a(16) =915a(17) =1028a(18) =1352a(19) =1508a(20) =1918a(21) =2105a(22) =3918a(23) =4181a(24) =5540a(25) =6396a(26) =6728a(27) =7250a(28) =9282a(29) =10100