# A150043 (b-file synthesized from sequence entry) 0 1 1 2 2 6 3 18 4 60 5 204 6 716 7 2560 8 9296 9 34128 10 126560 11 472864 12 1778016 13 6722880 14 25536768 15 97384128 16 372691968 17 1430618112 18 5506231808 19 21244025088 20 82137286400 21 318177976064 22 1234689470976 23 4798686523904 24 18676787597824 25 72786442978304 26 283997288733696 27 1109305183011840 28 4337384738945024