a(n) = 2*(2+n)! + 2^n.

Terms

a(0) =5a(1) =14a(2) =52a(3) =248a(4) =1456a(5) =10112a(6) =80704a(7) =725888a(8) =7257856a(9) =79834112a(10) =958004224a(11) =12454043648a(12) =174356586496