# A074033 (b-file synthesized from sequence entry) 1 1 2 0 3 1 4 4 5 15 6 40 7 144 8 512 9 1841 10 6528 11 23808 12 87380 13 322875 14 1198080 15 4473647 16 16777216 17 63164175 18 238605640 19 904200192 20 3435973836 21 13089461538 22 49977753600 23 191219367936 24 733007751680 25 2814750270420 26 10825959997440 27 41699995927744 28 160842843834660