

A123910


Numbers n such that n!!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
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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


LINKS

Table of n, a(n) for n=1..24.
Joe McLean, Interesting Sources of Probable Primes


MATHEMATICA

Do[f=n!!4; If[PrimeQ[f], Print[{n, f}]], {n, 1, 355}]


CROSSREFS

Cf. A007749, A094144.
Sequence in context: A108144 A241835 A279914 * A024886 A083249 A077153
Adjacent sequences: A123907 A123908 A123909 * A123911 A123912 A123913


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



