# A004141 (b-file synthesized from sequence entry) 1 1 2 2 3 8 4 48 5 256 6 1280 7 6912 8 39424 9 212992 10 1118208 11 6553600 12 36765696 13 199229440 14 1133117440 15 6499598336 16 36175872000 17 200655503360 18 1167945891840 19 6620826304512 20 36681168191488 21 212364657950720 22 1219998345330688 23 6864598984556544 24 38958828003262464 25 226089827240509440 26 1287455960675123200