cp's OEIS Frontend

A076680 Numbers k such that 4*k! + 1 is prime.

%I A076680 #30 Jul 05 2024 11:49:21
%S A076680 0,1,4,7,8,9,13,16,28,54,86,129,190,351,466,697,938,1510,2748,2878,
%T A076680 3396,4057,4384,5534,7069,10364
%N A076680 Numbers k such that 4*k! + 1 is prime.
%C A076680 a(25) > 6311. - _Jinyuan Wang_, Feb 06 2020
%H A076680 Factor Database, <a href="http://factordb.com/index.php?query=4*z%21%2B1&amp;perpage=200">Factors of the numbers 4z!+1</a>
%e A076680 k = 7 is a term because 4*7! + 1 = 20161 is prime.
%t A076680 Select[Range[5000],PrimeQ[4#!+1]&] (* _Harvey P. Dale_, Mar 23 2011 *)
%o A076680 (PARI) is(k) = ispseudoprime(4*k!+1); \\ _Jinyuan Wang_, Feb 06 2020
%Y A076680 Cf. m*n!-1 is a prime: A076133, A076134, A099350, A099351, A180627-A180631.
%Y A076680 Cf. m*n!+1 is a prime: A051915, A076679-A076683, A178488, A180626, A126896.
%Y A076680 Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205.
%Y A076680 Cf. n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071.
%K A076680 nonn,more
%O A076680 1,3
%A A076680 Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 25 2002
%E A076680 Corrected (added missed terms 2748, 2878) by _Serge Batalov_, Feb 24 2015
%E A076680 a(24) from _Jinyuan Wang_, Feb 06 2020
%E A076680 a(25)-a(26) from _Michael S. Branicky_, Jul 04 2024