# A046674 (b-file synthesized from sequence entry) 1 1 2 18 3 660 4 42000 5 4142880 6 586776960 7 113020427520 8 28432576972800 9 9056055981772800 10 3562946373482496000 11 1697172166720622592000 12 962691052768668647424000 13 641260394342965606809600000 14 495681727573700350908825600000 15 440084864982859007245221888000000