Number of permutations f of {1,...,n} such that 3^k + 3^(f(k)) - 1 is prime for every k = 1,...,n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =11a(4) =14a(5) =33a(6) =59a(7) =290a(8) =843a(9) =690a(10) =231a(11) =978a(12) =2896a(13) =2966a(14) =38252a(15) =384917a(16) =22351a(17) =68546a(18) =28245a(19) =147459a(20) =84578a(21) =17647a(22) =17647a(23) =232213a(24) =17647a(25) =792a(26) =93640a(27) =785178a(28) =5635699a(29) =11658279