# A151478 (b-file synthesized from sequence entry) 0 1 1 1 2 4 3 12 4 54 5 210 6 1020 7 4445 8 22610 9 105210 10 551376 11 2678676 12 14332164 13 71788860 14 389991888 15 1998530820 16 10984120290 17 57293297490 18 317798892840 19 1681213457352 20 9395215622364 21 50278804820244 22 282711201927336 23 1527524202392370 24 8633634028624332 25 47028406025950300 26 266981514041485600