a(n) is the smallest prime p such that p - 1 has 2*n divisors.

Terms

a(0) =3a(1) =7a(2) =13a(3) =31a(4) =113a(5) =61a(6) =193a(7) =211a(8) =181a(9) =241a(10) =13313a(11) =421a(12) =12289a(13) =2113a(14) =1009a(15) =1321a(16) =2424833a(17) =1801a(18) =786433a(19) =2161a(20) =4801a(21) =15361a(22) =155189249a(23) =2521a(24) =6481a(25) =61441a(26) =6301a(27) =8641a(28) =3489660929a(29) =12241