OFFSET
1,2
COMMENTS
Corresponding primes are: 257, 277, 487, 1267389841, ...
a(35) > 10^5.
Terms > 31 correspond to probable primes.
LINKS
Henri & Renaud Lifchitz, PRP Records. Search for n!4+256.
Joe McLean, Interesting Sources of Probable Primes
OpenPFGW Project, Primality Tester
EXAMPLE
11!4 + 2^8 = 11*7*3*1 + 256 = 487 is prime, so 11 is in the sequence.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 4] + 2^8] &]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 22 2017
EXTENSIONS
a(34) from Robert Price, Sep 25 2019
STATUS
approved