# A003474 (b-file synthesized from sequence entry) 1 1 2 4 3 18 4 32 5 160 6 324 7 1456 8 2048 9 13122 10 25600 11 117128 12 209952 13 913952 14 2119936 15 9447840 16 13107200 17 86093440 18 172186884 19 774840976 20 1310720000 21 6964002864 22 13718968384 23 62761410632 24 88159684608 25 557885504000 26 835308258304 27 5083731656658 28 8988257288192 29 45753584909920 30 89261680665600 31 411782264189296 32 564050001920000