# A002520 (b-file synthesized from sequence entry) 0 1 1 0 2 0 3 2240 4 98280 5 1790208 6 19138560 7 141920640 8 805208040 9 3723722240 10 14651449344 11 50573436480 12 156717687840 13 443691198720 14 1162883174400 15 2851049534592 16 6596666916840 17 14509544394240 18 30507984568320