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

0, 1, 4, 7, 8, 9, 13, 16, 28, 54, 86, 129, 190, 351, 466, 697, 938, 1510, 2748, 2878, 3396, 4057, 4384, 5534, 7069, 10364

Offset

1,3

Comments

a(25) > 6311. - Jinyuan Wang, Feb 06 2020

Links

Table of n, a(n) for n=1..26.

Factor Database, Factors of the numbers 4z!+1

Example

k = 7 is a term because 4*7! + 1 = 20161 is prime.

Mathematica

Select[Range[5000], PrimeQ[4#!+1]&] (* Harvey P. Dale, Mar 23 2011 *)

Prog

(PARI) is(k) = ispseudoprime(4*k!+1); \\ Jinyuan Wang, Feb 06 2020

Crossrefs

Cf. m*n!-1 is a prime: A076133, A076134, A099350, A099351, A180627-A180631.

Cf. m*n!+1 is a prime: A051915, A076679-A076683, A178488, A180626, A126896.

Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205.

Cf. n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071.

Sequence in context: A074231 A310938 A289631 * A235623 A001074 A214206

Adjacent sequences: A076677 A076678 A076679 * A076681 A076682 A076683

Keyword

nonn,more

Author

Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 25 2002

Extensions

Corrected (added missed terms 2748, 2878) by Serge Batalov, Feb 24 2015

a(24) from Jinyuan Wang, Feb 06 2020

a(25)-a(26) from Michael S. Branicky, Jul 04 2024

Status

approved