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%I #27 Sep 21 2015 20:39:21
%S 0,2,16,17,20,22,28,31,37,40,53,65,71,73,82,124,130,187,203,266,308,
%T 326,386,502,662,1919,3136,3229,4640,8113,8659,12307,20972,26408,49391
%N Numbers n such that n!!! + 3^n is prime.
%C n!!! is the triple factorial sometimes written n!3.
%C a(36) > 50000.
%e 2 is in the sequence because 2!!!+3^2 = 2+9 = 11 is prime.
%t MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
%t Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 3] + 3^#] &]
%Y Cf. A007661, A124248, A124249, A261316.
%K nonn
%O 1,2
%A _Robert Price_, Sep 09 2015