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%I #14 Jul 23 2023 17:00:44
%S 3,4,5,6,7,13,14,19,20,28,37,99,100,108,141,304,442,682,3641,4076
%N Numbers k such that A004154(k) - 1 is prime.
%C Some of the larger entries may only correspond to probable primes.
%t f[n_] := n!/10^Sum[ Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Do[ If[ PrimeQ[ f[n] - 1], Print[n]], {n, 1, 750}]
%Y Cf. A004154, A078154, A078203, A078190.
%K nonn,base,more
%O 1,1
%A _Cino Hilliard_, Dec 23 2002
%E Extended by _Robert G. Wilson v_ and _Jason Earls_, Dec 24 2002
%E a(19)-a(20) from _Michael S. Branicky_, Jul 23 2023
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