# A264927 (b-file synthesized from sequence entry) 0 1 1 1 2 4 3 18 4 81 5 396 6 1936 7 9416 8 45796 9 234972 10 1205604 11 6188328 12 31764496 13 162249168 14 828748944 15 4224034452 16 21529399441 17 113085801048 18 593996986944 19 3126735424128 20 16458794619136 21 86717178000000 22 456890625000000 23 2407551579000000 24 12686416153856064 25 66648950832253248 26 350144800010358336 27 1838080630013808960 28 9648980656951105600 29 50559912359694495680