# A002463 (b-file synthesized from sequence entry) 1 1 2 3 3 30 4 175 5 4410 6 29106 7 396396 8 2760615 9 156434850 10 1122854590 11 16291599324 12 119224885962 13 3515605611700 14 26077294372500 15 388924218927000 16 2913690606794775 17 350671234206006450 18 2647224022927695750 19 40095381399899017500 20 304513870316075169750