A076134 Numbers k such that 3*k! - 1 is prime.

0, 1, 2, 3, 4, 5, 9, 12, 17, 26, 76, 379, 438, 1695, 6709, 13313, 18504, 19021, 24488, 45552, 49085

Offset

1,3

Comments

a(22) > 50000. - Roger Karpin, Nov 13 2016

Links

Table of n, a(n) for n=1..21.

Example

k = 5 is here because 3*5! - 1 = 359 is prime.

Maple

for n from 0 to 1000 do if isprime(3*n! - 1) then print(n) end if end do;

Mathematica

Select[Range[0, 10^3], PrimeQ[3 #! - 1] &] (* Robert Price, May 27 2019 *)

Prog

(PARI) isok(n) = isprime(3*n! - 1); \\ Michel Marcus, Nov 13 2016
(PFGW) ABC2 3*$a!+1
a: from 1 to 1000 // Jinyuan Wang, Feb 04 2020

Crossrefs

Cf. A051915, A076134.

Cf. A002982, A076133, A099350, A099351, A180627, A180628, A180629, A180630, A180631.

Sequence in context: A084542 A038201 A033084 * A239742 A101526 A264994

Adjacent sequences: A076131 A076132 A076133 * A076135 A076136 A076137

Keyword

nonn,more

Author

Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 30 2002

Extensions

a(15)-a(21) from Roger Karpin, Nov 13 2016

Status

approved