Primes of the form 5*2^k + 3.

Terms

a(0) =13a(1) =23a(2) =43a(3) =83a(4) =163a(5) =643a(6) =1283a(7) =10243a(8) =20483a(9) =1310723a(10) =5242883a(11) =335544323a(12) =1342177283a(13) =21474836483a(14) =85899345923