cp's OEIS Frontend

A099351 Numbers k such that 5*k! - 1 is prime.

%I A099351 #33 Jul 12 2024 19:58:59
%S A099351 3,5,8,13,20,25,51,97,101,241,266,521,1279,1750,2204,2473,4193,5181,
%T A099351 10080
%N A099351 Numbers k such that 5*k! - 1 is prime.
%C A099351 a(15) > 1879. - _Jinyuan Wang_, Feb 04 2020
%C A099351 a(17) > 3500. - _Michael S. Branicky_, Mar 06 2021
%H A099351 <a href="/index/Pri#primepop">Index entries for sequences related to numbers of primes of the form k*n!+-1</a>
%e A099351 k = 5 is here because 5*5! - 1 = 599 is prime.
%p A099351 for n from 0 to 1000 do if isprime(5*n! - 1) then print(n) end if end do;
%t A099351 Select[Range[550],PrimeQ[5#!-1]&] (* _Harvey P. Dale_, Nov 27 2013 *)
%o A099351 (PARI) is(n)=ispseudoprime(5*n!-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%o A099351 (Python)
%o A099351 from sympy import isprime
%o A099351 from math import factorial
%o A099351 print([k for k in range(300) if isprime(5*factorial(k) - 1)]) # _Michael S. Branicky_, Mar 05 2021
%Y A099351 Cf. A002982, A076133, A076134, A099350, A180627, A180628, A180629, A180630, A180631.
%K A099351 nonn,more
%O A099351 1,1
%A A099351 _Brian Kell_, Oct 12 2004
%E A099351 a(13)-a(14) from _Jinyuan Wang_, Feb 04 2020
%E A099351 a(15)-a(16) from _Michael S. Branicky_, Mar 05 2021
%E A099351 a(17)-a(18) from _Michael S. Branicky_, Apr 03 2023
%E A099351 a(19) from _Michael S. Branicky_, Jul 12 2024