# A070734 (b-file synthesized from sequence entry) 3 3 4 24 5 60 6 720 7 2520 8 40320 9 181440 10 3628800 11 19958400 12 479001600 13 3113510400 14 87178291200 15 653837184000 16 20922789888000 17 177843714048000 18 6402373705728000 19 60822550204416000 20 2432902008176640000