Number of permutations f of {1,...,n} such that k!*f(k) + 1 is prime for every k from 1 to n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =10a(5) =10a(6) =13a(7) =40a(8) =212a(9) =702a(10) =3531a(11) =19008a(12) =34858a(13) =39764a(14) =102312a(15) =47927a(16) =94860a(17) =232006a(18) =658766a(19) =829583a(20) =1547703a(21) =2040211a(22) =32073218a(23) =51347260a(24) =496226762a(25) =1504307318a(26) =16663026685a(27) =125080784519a(28) =241032642271