A258616 Numbers n such that n!!-16 is prime.

7, 9, 13, 17, 25, 185, 197, 261, 407, 593, 1535, 2129, 2139, 2581, 4133, 4665, 15787, 25337, 27449

Offset

1,1

Comments

Corresponding primes are 89, 929, 135119, 34459409, ... .

a(20) > 50000.

Links

Table of n, a(n) for n=1..19.

Joe McLean, Interesting Sources of Probable Primes

Mathematica

Select[Range[4, 1000], PrimeQ[#!!-16]&] (* Robert Price, Jun 05 2015 *)
Do[f=n!! - 16; If[PrimeQ[f], Print[{n, f}]], {n, 4, 600}] (* Vincenzo Librandi, Jun 06 2015 *) (see comment)

Crossrefs

Cf. A006882, A007749, A094144, A123910.

Sequence in context: A329166 A222945 A129069 * A125866 A027692 A343001

Adjacent sequences: A258613 A258614 A258615 * A258617 A258618 A258619

Keyword

hard,more,nonn

Author

Robert Price, Jun 05 2015

Status

approved