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A124249
Numbers n such that n!! - 2^n is prime.
3
9, 13, 21, 25, 27, 35, 41, 53, 63, 81, 123, 333, 381, 413, 1187, 2265, 3153, 4211, 4887, 7359, 14161, 14643, 17299, 22107, 31487, 40235, 46711
OFFSET
1,1
COMMENTS
All terms are odd.
a(28) > 50000. - Robert Price, Sep 04 2015
EXAMPLE
9 is in the sequence because 9!! - 2^9 = 433 is prime.
MATHEMATICA
Select[Range[0, 50000], #!! - 2^# > 0 && PrimeQ[#!! - 2^#] &] (* Robert Price, Sep 04 2015 *)
CROSSREFS
Cf. A124248.
Sequence in context: A026045 A371728 A304259 * A137168 A033870 A151901
KEYWORD
more,nonn
AUTHOR
Farideh Firoozbakht, Nov 27 2006
EXTENSIONS
Three more terms from Ryan Propper, Nov 05 2007
a(21)-a(27) from Robert Price, Sep 04 2015
STATUS
approved