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A139202
Numbers k such that (k!-7)/7 is prime.
3
7, 9, 20, 23, 46, 54, 57, 71, 85, 387, 396, 606, 1121, 2484, 6786, 9321, 11881, 18372
OFFSET
1,1
COMMENTS
a(19) > 25000. - Robert Price, Nov 05 2016
MATHEMATICA
a = {}; Do[If[PrimeQ[(n! - 7)/7], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (*Artur Jasinski*)
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Artur Jasinski, Apr 11 2008
EXTENSIONS
More terms from Alexis Olson (AlexisOlson(AT)gmail.com), Nov 14 2008
a(13)-a(14) PRPs from Sean A. Irvine, Aug 05 2010
a(15)-a(18) PRP from Robert Price, Nov 05 2016
STATUS
approved