A319224
Integers q for which f(q) = ((((q - 2)! - 1) / q) - 1) / (q + 1) is a prime number.
Original entry on oeis.org
7, 11, 19, 61, 2557
Offset: 1
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a[q_]:=If[PrimeQ[((((q - 2)! - 1) / q) - 1) / (q + 1)], q]; DeleteCases[Array[a, 100], Null] (* Stefano Spezia, Nov 04 2018 *)
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forprime(q=7, 2557, my(p = ((((q - 2)! - 1) / q) - 1) / (q + 1)); if(ispseudoprime(p), print1(q, ", ")))
A319304
Integers q for which f(q) = ((((q - 1)! + 1) / q) + 1) / (q + 1) is a prime number.
Original entry on oeis.org
7, 17, 31, 67, 89
Offset: 1
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[n: n in [1..100] | IsPrime(n) and IsPrime((((Factorial(n-1)+1) div n)+1) div (n+1))]; // Vincenzo Librandi, Sep 21 2018
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Select[Prime[Range[100]], PrimeQ[((((# - 1)! + 1) / #) + 1) / (# + 1)] &] (* Vincenzo Librandi, Sep 21 2018 *)
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forprime(q=7, 89, my(p = ((((q - 1)! + 1) / q) + 1) / (q + 1)); if(ispseudoprime(p), print1(q, ", ")))
1621 and 1699, which do not belong here, removed by
Rashid Naimi, Mar 21 2019
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