# A375799 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 6 4 36 5 240 6 1800 7 16800 8 178080 9 2086560 10 27518400 11 399168000 12 6286896000 13 107623676160 14 1984274772480 15 39143052748800 16 824445099878400 17 18450791322163200 18 437015358530150400 19 10929450232744243200 20 287728555881102336000 21 7952251084537503744000