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

Terms

a(0) =1a(1) =5a(2) =65a(3) =377a(4) =1189a(5) =1469a(6) =25805a(7) =58589a(8) =134945a(9) =137345a(10) =170585a(11) =272609a(12) =285389a(13) =420209a(14) =538733a(15) =592409a(16) =618449a(17) =680705a(18) =778805a(19) =1163065a(20) =1520441a(21) =1700945a(22) =2099201a(23) =2831009a(24) =4020029a(25) =4174169a(26) =4516109a(27) =5059889a(28) =5215769