Primes of the form 2^k + 21.A156983Primes of the form 2^k + 21.Terms a(0) =23a(1) =29a(2) =37a(3) =53a(4) =149a(5) =277a(6) =2069a(7) =32789a(8) =65557a(9) =524309External referencesoeis: A156983