

A202426


Numbers n such that n!*n!!  1 is prime.


1



2, 3, 4, 10, 11, 13, 17, 22, 26, 36, 79, 196
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

No additional terms up to n=1000.  Harvey P. Dale, Oct 29 2016


LINKS

Table of n, a(n) for n=1..12.


EXAMPLE

for n = 4, 4!*4!! + 1 = 24*8  1 = 191 is prime.


MATHEMATICA

lst={}; Do[If[PrimeQ[n!*n!!1], AppendTo[lst, n]], {n, 500}]; lst
Select[Range[200], PrimeQ[#!#!!1]&] (* Harvey P. Dale, Oct 29 2016 *)


PROG

(MAGMA) a:=func< n  Factorial(n)*(&*[n..2 by 2])1 >; [ n: n in [0..660]  IsPrime(a(n)) ]; // Bruno Berselli, Dec 19 2011


CROSSREFS

Cf. A000142, A006882, A202424 (associated primes).
Sequence in context: A080897 A117383 A047455 * A039002 A295393 A120023
Adjacent sequences: A202423 A202424 A202425 * A202427 A202428 A202429


KEYWORD

nonn


AUTHOR

Michel Lagneau, Dec 19 2011


STATUS

approved



