Sum of divisors of 2^prime(n)-1.

Terms

a(0) =4a(1) =8a(2) =32a(3) =128a(4) =2160a(5) =8192a(6) =131072a(7) =524288a(8) =8567136a(9) =539922240a(10) =2147483648a(11) =138055271872