Primes p such that sigma((p + 1) / 2) is a prime q.

Terms

a(0) =3a(1) =7a(2) =17a(3) =31a(4) =127a(5) =577a(6) =3361a(7) =4801a(8) =6961a(9) =8191a(10) =31249a(11) =131071a(12) =171697a(13) =524287a(14) =982801a(15) =1062881a(16) =1104097a(17) =1367857a(18) =1407841a(19) =1468897a(20) =2705137a(21) =3770257a(22) =6822817a(23) =7785457a(24) =10941841a(25) =14183137a(26) =15557041a(27) =18495361a(28) =20749681a(29) =25304497