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%I #10 Jul 15 2021 10:18:42
%S 2,5,9,10,13,14,22,25,50,66,125,250,293,314,349,1622,1642,2937,2966,
%T 3841,4298,4898,5270
%N Numbers k such that the sum of the first k double factorials (1!! + 2!! + ... + k!!) is prime.
%C a(18) must be greater than 2300. The sum of the first 1642 double factorials is a (probable) prime with 2286 digits.
%C Numbers corresponding to a(18)-a(23) are probable primes. - _Farideh Firoozbakht_, May 16 2010
%e 5 belongs since 1!! + 2!! + 3!! + 4!! + 5!! = 29, a prime.
%Y Cf. A114410, A079078.
%K nonn
%O 1,1
%A _Giovanni Resta_, Feb 23 2006
%E a(18)-a(23) from _Farideh Firoozbakht_, May 16 2010
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