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 A099351 Numbers k such that 5*k! - 1 is prime. 10
 3, 5, 8, 13, 20, 25, 51, 97, 101, 241, 266, 521, 1279, 1750, 2204, 2473 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(15) > 1879. - Jinyuan Wang, Feb 04 2020 a(17) > 3500. - Michael S. Branicky, Mar 06 2021 LINKS EXAMPLE k = 5 is here because 5*5! - 1 = 599 is prime. MAPLE for n from 0 to 1000 do if isprime(5*n! - 1) then print(n) end if end do; MATHEMATICA Select[Range[550], PrimeQ[5#!-1]&] (* Harvey P. Dale, Nov 27 2013 *) PROG (PARI) is(n)=ispseudoprime(5*n!-1) \\ Charles R Greathouse IV, Jun 13 2017 (Python) from sympy import isprime from math import factorial print([k for k in range(300) if isprime(5*factorial(k) - 1)]) # Michael S. Branicky, Mar 05 2021 CROSSREFS Cf. A002982, A076133, A076134, A099350, A180627, A180628, A180629, A180630, A180631. Sequence in context: A035421 A035424 A245934 * A265065 A265066 A265067 Adjacent sequences:  A099348 A099349 A099350 * A099352 A099353 A099354 KEYWORD nonn,more AUTHOR Brian Kell, Oct 12 2004 EXTENSIONS a(13)-a(14) from Jinyuan Wang, Feb 04 2020 a(15)-a(16) from Michael S. Branicky, Mar 05 2021 STATUS approved

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Last modified May 11 01:55 EDT 2021. Contains 343784 sequences. (Running on oeis4.)