Primes that remain prime through 4 iterations of function f(x) = 2x + 1.

Terms

a(0) =2a(1) =89a(2) =179a(3) =53639a(4) =53849a(5) =61409a(6) =63419a(7) =66749a(8) =126839a(9) =127139a(10) =143609a(11) =167729a(12) =186149a(13) =206369a(14) =254279a(15) =268049a(16) =296099a(17) =340919a(18) =405269a(19) =422069a(20) =446609a(21) =539009a(22) =594449a(23) =607319a(24) =658349a(25) =671249a(26) =725009a(27) =775949a(28) =810539a(29) =810809