Numbers m such that 4^(m-1) == 1 (mod (m-1)^2 + 1).

Terms

a(0) =1a(1) =3a(2) =5a(3) =17a(4) =217a(5) =257a(6) =387a(7) =8209a(8) =20137a(9) =37025a(10) =59141a(11) =65537a(12) =283801a(13) =649801a(14) =1382401a(15) =373164545a(16) =535019101a(17) =2453039425a(18) =4294967297