Indices of the prime factors of Fermat numbers in the sequence of primes.

Terms

a(0) =2a(1) =3a(2) =7a(3) =55a(4) =116a(5) =6543a(6) =10847a(7) =23974a(8) =27567a(9) =76709a(10) =177975a(11) =457523a(12) =887643a(13) =1625567a(14) =2751966a(15) =3772007a(16) =9385401a(17) =42401669a(18) =61136051a(19) =301137372a(20) =2946723445a(21) =7632981296a(22) =24728168164a(23) =98261951745a(24) =99582868271a(25) =159657063059a(26) =231641062432a(27) =851793186025a(28) =870658222248