Primes of the form 2^n*(n+1)!+1.
a(12) = 2^118*119!+1, a(13) = 2^142*143!+1. I conjecture that a(13) is the last prime number of this form.  Jorge Coveiro, Apr 01 2004
Conjecture that a(13) is the last prime of this form is false:
a(14) = 2^2789*2780!+1 is prime
a(15) = 2^3142*3143!+1 is prime
a(16) = 2^3557*3558!+1 is prime
a(17) = 2^3686*3687!+1 is prime
a(18) = 2^4190*4191!+1 is prime
a(19) = 2^7328*7329!+1 is prime
See A248879.  Robert Price, Mar 10 2015
