a(n) = floor(exp(19/24)*n!).

Terms

a(0) =2a(1) =4a(2) =13a(3) =52a(4) =264a(5) =1589a(6) =11123a(7) =88989a(8) =800902a(9) =8009022a(10) =88099244a(11) =1057190930a(12) =13743482102a(13) =192408749440