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A290116 Primes of the form k! / 2 - 1. 1

%I

%S 2,11,59,359,181439,4111419327088961408862781439999999,

%T 16726263306581903554085031026720375832575999999999

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

%H Robert Price, <a href="/A290116/b290116.txt">Table of n, a(n) for n = 1..7</a>

%H Joe McLean, <a href="http://web.archive.org/web/20091027034731/http://uk.geocities.com/nassarawa%40btinternet.com/probprim2.htm">Interesting Sources of Probable Primes</a>

%H OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>

%F a = (A082671(n)!-2)/2.

%e 6! / 2 - 1 = 359, which is prime, so 359 is in the sequence.

%e 7! / 2 - 1 = 2519 = 11 * 229, so 2519 is not in the sequence.

%t Select[Table[k! / 2 - 1, {k, 2, 100}], PrimeQ[#]&]

%Y Cf. A082671, A139172.

%K nonn

%O 1,1

%A _Robert Price_, Jul 19 2017

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Last modified October 18 08:19 EDT 2021. Contains 348066 sequences. (Running on oeis4.)