# A004246 (b-file synthesized from sequence entry) 4 8 5 25 6 144 7 735 8 4608 9 39285 10 362000 11 3628185 12 40808448 13 478988081 14 6227101888 15 87248724750 16 1300561920000 17 20922788404479 18 355587467242752 19 6402373698206889 20 121810906419200000