# A069053 (b-file synthesized from sequence entry) 1 1 2 4 3 36 4 144 5 3600 6 10800 7 529200 8 2116800 9 6350400 10 6350400 11 768398400 12 768398400 13 129859329600 14 129859329600 15 129859329600 16 519437318400 17 150117385017600 18 450352155052800 19 162577127974060800 20 6503085118962432