# A225178 (b-file synthesized from sequence entry) 1 1 2 2 3 6 4 16 5 48 6 140 7 408 8 1224 9 3640 10 10824 11 32192 12 96576 13 288912 14 864288 15 2585584 16 7735104 17 23205312 18 69551552 19 208461504 20 624806688 21 1872691488 22 5612903296 23 16838709888 24 50500659456 25 151455567744 26 454227600128 27 1362265877376