# A065804 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 4 4 6 5 7 6 24 7 120 8 9 9 40320 10 11 11 3628800 12 13 13 479001600 14 15 15 87178291200 16 17 17 20922789888000 18 19 19 6402373705728000 20 21 21 2432902008176640000 22 23 23 1124000727777607680000 24 720 25 26 26 15511210043330985984000000 27 28