2^n minus the sum of the proper divisors of n.

Terms

a(0) =2a(1) =3a(2) =7a(3) =13a(4) =31a(5) =58a(6) =127a(7) =249a(8) =508a(9) =1016a(10) =2047a(11) =4080a(12) =8191a(13) =16374a(14) =32759a(15) =65521a(16) =131071a(17) =262123a(18) =524287a(19) =1048554a(20) =2097141a(21) =4194290a(22) =8388607a(23) =16777180a(24) =33554426a(25) =67108848a(26) =134217715a(27) =268435428a(28) =536870911a(29) =1073741782