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 A303737 Numbers k such that (2*k)! + k! - 1 is prime. 1
 1, 4, 18, 49, 60, 82, 321, 6328 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(9) > 10000. - Giovanni Resta, Jun 07 2018 LINKS EXAMPLE 1 is a term because (2*1)! + 1! - 1 = 2 which is a prime. 4 is a term because (2*4)! + 4! - 1 = 40343 which is a prime. MAPLE select(k->isprime(factorial(2*k)+factorial(k)-1), [\$1..1000]); PROG (PARI) isok(k) = isprime((2*k)! + k! - 1); \\ Michel Marcus, May 28 2018 CROSSREFS Cf. A242487, A300947, A303738 (corresponding primes). Sequence in context: A081528 A056147 A181857 * A180805 A120656 A256431 Adjacent sequences:  A303734 A303735 A303736 * A303738 A303739 A303740 KEYWORD nonn,more AUTHOR Muniru A Asiru, May 27 2018 EXTENSIONS a(8) from Giovanni Resta, Jun 07 2018 STATUS approved

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Last modified March 29 17:23 EDT 2020. Contains 333116 sequences. (Running on oeis4.)