a(n) = 2^(n - 1) - prime(n).

Terms

a(0) =-1a(1) =-1a(2) =-1a(3) =1a(4) =5a(5) =19a(6) =47a(7) =109a(8) =233a(9) =483a(10) =993a(11) =2011a(12) =4055a(13) =8149a(14) =16337a(15) =32715a(16) =65477a(17) =131011a(18) =262077a(19) =524217a(20) =1048503a(21) =2097073a(22) =4194221a(23) =8388519a(24) =16777119a(25) =33554331a(26) =67108761a(27) =134217621a(28) =268435347a(29) =536870799