login
A123910
Numbers k such that k!!-4 is prime.
51
5, 7, 9, 11, 13, 15, 19, 25, 35, 79, 81, 105, 171, 243, 271, 295, 355, 523, 591, 1211, 3073, 11157, 12887, 19825
OFFSET
1,1
COMMENTS
Corresponding primes of the form k!!-4 = a(n)!!-4 are {11, 101, 941, 10391, 135131, 2027021, 654729071, 7905853580621, 221643095476699771871, ...}.
a(25) > 50000. - Robert Price, May 08 2015
MATHEMATICA
Do[f=n!!-4; If[PrimeQ[f], Print[{n, f}]], {n, 1, 355}]
CROSSREFS
Sequence in context: A108144 A241835 A279914 * A024886 A083249 A077153
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Oct 28 2006
EXTENSIONS
More terms from Farideh Firoozbakht, Nov 19 2006
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
a(23)-a(24) from Robert Price, May 08 2015
STATUS
approved