a(n) = 6*n! - 1.

Terms

a(0) =5a(1) =5a(2) =11a(3) =35a(4) =143a(5) =719a(6) =4319a(7) =30239a(8) =241919a(9) =2177279a(10) =21772799a(11) =239500799a(12) =2874009599a(13) =37362124799a(14) =523069747199