Numbers k such that sigma((k + 1) / 2) is a prime q.

Terms

a(0) =3a(1) =7a(2) =17a(3) =31a(4) =49a(5) =127a(6) =577a(7) =1457a(8) =3361a(9) =4801a(10) =6961a(11) =8191a(12) =10081a(13) =15841a(14) =20401a(15) =31249a(16) =34321a(17) =55777a(18) =57121a(19) =59857a(20) =131071a(21) =167041a(22) =171697a(23) =293377a(24) =524287a(25) =559681a(26) =916657a(27) =982801a(28) =1062881a(29) =1104097