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Numbers n such that (n!/n#)^2 + 1 is prime, where n# = primorial numbers (A034386).
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%I #3 Dec 15 2017 17:36:51

%S 1,2,3,4,5,6,7,12,13,22,23,39,50,54,60,61,69,182,620,767,1308,5129

%N Numbers n such that (n!/n#)^2 + 1 is prime, where n# = primorial numbers (A034386).

%C n!/n# is known as n compositorial. All values have been proved prime. Primality proof for the largest, which has 29223 digits: PFGW Version 1.2.0 for Windows [FFT v23.8] Primality testing (5129!/5129#)^2+1 [N-1, Brillhart-Lehmer-Selfridge] Running N-1 test using base 2591 Calling Brillhart-Lehmer-Selfridge with factored part 33.59% (5129!/5129#)^2+1 is prime! (164.5911s+0.0122s)

%K more,nonn

%O 1,2

%A _Jason Earls_, Jul 21 2005