cp's OEIS Frontend

A093155 Primes resulting from serial multiplication of even composites, minus 1.

%I A093155 #31 Sep 08 2022 08:45:13
%S A093155 3,23,191,23039,322559,5160959,40874803199,25505877196799
%N A093155 Primes resulting from serial multiplication of even composites, minus 1.
%C A093155 Primes of the form 2^n*(n+1)! - 1.
%C A093155 a(9) has 193 digits, a(10) has 230 digits. - _Vincenzo Librandi_, Mar 08 2015
%F A093155 Starting with 4, multiply even composites until the product minus 1 equals a prime.
%e A093155 a(1) = 3 = 2*2! - 1.
%e A093155 a(2) = 23 = 2^2*3! - 1.
%e A093155 a(3) = 191 = 2^3*4! - 1.
%e A093155 a(4) = 23039 = 2^5*6! - 1.
%e A093155 a(5) = 322559 = 2^6*7! - 1.
%e A093155 a(6) = 5160959 = 2^7*8! - 1.
%e A093155 a(7) = 40874803199 = 2^10*11! - 1.
%e A093155 a(8) = 25505877196799 = 2^12*13! - 1.
%e A093155 a(9) = 2^101*102! - 1 is too large to include.
%e A093155 a(10) = 2^117*118! - 1; a(11) = 2^227*228! - 1. - _Jorge Coveiro_, Dec 24 2004
%t A093155 Select[Table[2^n (n + 1)! - 1, {n, 0, 300}], PrimeQ] (* _Vincenzo Librandi_, Mar 08 2015 *)
%o A093155 (PARI) for(x=1,500,if(isprime(2^x*(x+1)!-1),print1(x, ", "))) \\ _Jorge Coveiro_, Dec 24 2004
%o A093155 (Magma) [a: n in [0..100] | IsPrime(a) where a is 2^n*Factorial(n+1)-1]; // _Vincenzo Librandi_, Mar 08 2015
%Y A093155 Cf. A093154, A101323.
%K A093155 easy,nonn
%O A093155 1,1
%A A093155 _Enoch Haga_, Mar 25 2004
%E A093155 Edited by _Ray Chandler_, Mar 27 2004
%E A093155 The next term is too large to include.