Primes of the form 2^k + 2k - 1.A173168Primes of the form 2^k + 2k - 1.Terms a(0) =3a(1) =7a(2) =13a(3) =23a(4) =41a(5) =271a(6) =2069a(7) =16411a(8) =32797a(9) =134217781External referencesoeis: A173168