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A139205 Numbers k such that (k!-10)/10 is prime. 20

%I #10 Dec 23 2016 21:44:44

%S 5,6,7,11,13,17,28,81,87,433,640,647,798,1026,1216,1277,3825,6684

%N Numbers k such that (k!-10)/10 is prime.

%C a(19) > 25000. - _Robert Price_, Dec 23 2016

%t a = {}; Do[If[PrimeQ[(n! - 10)/10], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (*Artur Jasinski*)

%t Select[Range[700],PrimeQ[(#!-10)/10]&] (* _Harvey P. Dale_, Feb 15 2015 *)

%Y Cf. A139189, A139190, A139191, A139192, A139193, A139194, A139195, A139196, A139197, A139198.

%Y Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

%K hard,more,nonn

%O 1,1

%A _Artur Jasinski_, Apr 11 2008

%E One additional term (a(12)) from _Harvey P. Dale_, Feb 15 2015

%E More terms from _Serge Batalov_, Feb 18 2015

%E a(18) from _Robert Price_, Dec 23 2016

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Last modified March 29 10:59 EDT 2024. Contains 371277 sequences. (Running on oeis4.)