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%I #8 Jul 17 2021 01:45:30
%S 4,6,8,14,18,28,64,324,778,882
%N Numbers k such that k! - k!! + 1 is prime, where k!! denotes double factorial (A001147).
%C Next term is greater than 3000.
%e 6! - 6!! + 1 = 673, which is prime.
%t Select[Range[900],PrimeQ[#!-#!!+1]&] (* _Harvey P. Dale_, Mar 27 2015 *)
%Y Cf. A000142, A001147, A116896.
%K hard,more,nonn
%O 1,1
%A _Giovanni Resta_, Mar 04 2006
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