A265114 Numbers n such that n!! - 2^8 is prime.

11, 15, 21, 27, 31, 53, 59, 71, 87, 91, 99, 129, 219, 337, 507, 695, 893, 1033, 1961, 2381, 3237, 3485, 6151, 8981, 17873, 18163, 33621, 38543

Offset

1,1

Comments

Corresponding primes are 10139, 2026769, 13749310319, 213458046676619, 191898783962510369, ...

a(29) > 50000. - Robert Price, May 08 2015

Links

Table of n, a(n) for n=1..28.

Joe McLean, Interesting Sources of Probable Primes

Mathematica

Select[Range[8, 50000], PrimeQ[#!! - 256] &]

Prog

(PARI) is(n)=ispseudoprime(n!! - 2^8) \\ Anders Hellström, Dec 02 2015
(PARI) df(n) = if( n<0, 0, my(E); E = exp(x^2 / 2 + x * O(x^n)); n! * polcoeff( 1 + E * x * (1 + intformal(1 / E)), n));
for(n=1, 1e3, if(ispseudoprime(df(n) - 2^8), print1(n , ", "))) \\  Altug Alkan, Dec 03 2015

Crossrefs

Cf. A007749, A094144.

Sequence in context: A105179 A120156 A237278 * A213179 A211322 A087682

Adjacent sequences: A265111 A265112 A265113 * A265115 A265116 A265117

Keyword

hard,more,nonn

Author

Robert Price, Dec 01 2015

Status

approved