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

Terms

a(0) =1a(1) =3a(2) =15a(3) =35a(4) =119a(5) =255a(6) =455a(7) =1295a(8) =2555a(9) =2703a(10) =3815a(11) =3855a(12) =4355a(13) =5543a(14) =6479a(15) =8007a(16) =9215a(17) =10439a(18) =10619a(19) =11951a(20) =16211a(21) =22895a(22) =23435a(23) =26319a(24) =26795a(25) =27839a(26) =28679a(27) =35207a(28) =43055a(29) =44099