# A066410 (b-file synthesized from sequence entry) 1 15 2 252 3 3048 4 34560 5 403200 6 4390848 7 45732192 8 487710720 9 5079674880 10 52124083200 11 542890252800 12 5618427494400 13 58517854617600 14 591272607744000 15 6026281863275520 16 60762014342184960 17 623846047297536000 18 6394202229664972800 19 64417520701204070400 20 652677739551129600000