# A046984 (b-file synthesized from sequence entry) 0 1 1 4 2 18 3 88 4 468 5 2672 6 16072 7 100064 8 636368 9 4097984 10 26579488 11 173093760 12 1129796928 13 7383588608 14 48287978624 15 315921649152 16 2067346607360 17 13530037877760 18 88555066819072 19 579620448450560 20 3793872862974976 21 24832858496561152 22 162544900186359808