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A273932 Integers n such that ceiling(sqrt(n!)) is prime. 0

%I

%S 2,3,4,5,7,21,2132,3084,9301

%N Integers n such that ceiling(sqrt(n!)) is prime.

%C This sequence includes the known solutions of Brocard's problem as of 2016 (see A146968).

%e 3 is in the sequence because 3! = 6, sqrt(6) = 2.449489742783178..., the ceiling of which is 3, which is prime.

%e 4 is in the sequence because 4! = 24, sqrt(24) = 4.898979485566356..., the ceiling of which is 5, which is prime.

%t Select[Range[3200]], PrimeQ[Ceiling[Sqrt[#!]]] &]

%Y Cf. A055228 (ceiling(sqrt(n!))), A146968.

%K nonn,more

%O 1,1

%A _Salvador Cerdá_, Jun 04 2016

%E a(9) from _Giovanni Resta_, Jun 20 2016

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Last modified August 15 16:02 EDT 2020. Contains 336505 sequences. (Running on oeis4.)