# A000760 (b-file synthesized from sequence entry) 1 1 2 8 3 40 4 176 5 748 6 3248 7 14280 8 63768 9 285296 10 1285688 11 5794436 12 26261224 13 119028156 14 541876608 15 2466620624 16 11267536496 17 51458718144 18 235690960392 19 1079212461992 20 4953659984000 21 22730713367468 22 104520944666808