a(n) is the least number k such that prime(k) - 1 is divisible by 2^(n-1) and the quotient is odd.

Terms

a(0) =1a(1) =2a(2) =3a(3) =13a(4) =7a(5) =25a(6) =44a(7) =116a(8) =55a(9) =974a(10) =1581a(11) =2111a(12) =1470a(13) =4289a(14) =10847a(15) =15000a(16) =6543a(17) =91466a(18) =62947a(19) =397907a(20) =498178a(21) =1452314a(22) =6025010a(23) =20197904a(24) =38946356a(25) =9385401a(26) =24843812a(27) =98842359a(28) =166808880a(29) =556542914