A262772 Numbers k such that k!! - 32 is prime.

7, 45, 67, 145, 411, 825, 1021, 4039, 9069, 9789, 12463, 15137, 26313, 27499

Offset: 1

Author

Robert Price, Sep 30 2015

Keywords

• hard
• more
• nonn

Comments

Corresponding primes are 73, 25373791335626257947657609343, ... .

a(15) > 50000.

Links

• Joe McLean, Interesting Sources of Probable Primes

Crossrefs

Cf. A006882, A007749, A094144, A123910, A258616.

Programs

Magma

DoubleFactorial:=func< n | &*[n..2 by -2] >; [ n: n in [7..450] | IsPrime(DoubleFactorial(n) -32) ]; // Vincenzo Librandi, Oct 01 2015

Mathematica

Select[Range[0, 50000], If[#!! - 32 > 0, PrimeQ[#!! - 32]] &]

PARI

for(n=1, 1e4, if (isprime(prod(k=0, (n-1)\2, n - 2*k ) - 32),print1(n", "))) \\ Altug Alkan, Oct 01 2015