A186450 - OEIS

%I #4 Mar 30 2012 18:35:54

%S 2,5,13,151,5167,39918847

%N Primes of the form k! + 2^k - 1.

%C a(7) = 167! + 2^167 - 1 = 1503616514 ... 959365500927 has 301 digits ;

%C a(8) = 2609! + 2^2609 - 1 = 4110644622 ... 780469952511 has 7783 digits.

%e for k=3, 13 is in the sequence because 3! + 2^3 - 1 = 13 is prime.

%t lst={}; Do[ q=k!+2^k-1; If[PrimeQ[q], AppendTo[lst, q]], {k, 0, 400}]; lst

%Y Cf. A186449.

%K nonn

%O 1,1

%A _Michel Lagneau_, Feb 22 2011