Primes of the form 2^r * 11^s - 1.

Terms

a(0) =3a(1) =7a(2) =31a(3) =43a(4) =127a(5) =241a(6) =967a(7) =5323a(8) =8191a(9) =117127a(10) =131071a(11) =524287a(12) =7496191a(13) =10307263a(14) =77948683a(15) =253755391a(16) =428717761a(17) =738197503a(18) =1714871047a(19) =2147483647a(20) =16240345087a(21) =27437936767a(22) =42218553343