# A003498 (b-file synthesized from sequence entry) 0 1 1 12 2 48 3 252 4 1440 5 8544 6 52416 7 330588 8 2130240 9 13961808 10 92784384 11 623772288 12 4234688640 13 28990262016 14 199908428544 15 1387276513308 16 9681052037760 17 67895140257840 18 478281284627328 19 3382695596455344