Smallest Sophie Germain prime >= 2^n.

Terms

a(0) =2a(1) =2a(2) =5a(3) =11a(4) =23a(5) =41a(6) =83a(7) =131a(8) =281a(9) =593a(10) =1031a(11) =2063a(12) =4211a(13) =8243a(14) =16421a(15) =32771a(16) =65633a(17) =131321a(18) =262193a(19) =524351a(20) =1048889a(21) =2097629a(22) =4194581a(23) =8388953a(24) =16777259a(25) =33554771a(26) =67108913a(27) =134218433a(28) =268435631a(29) =536871311