# A097681 (b-file synthesized from sequence entry) 0 1 1 6 2 36 3 216 4 1296 5 7776 6 47376 7 314496 8 2612736 9 28740096 10 368395776 11 4796983296 12 60300205056 13 750367328256 14 10151357239296 15 164475953381376 16 3110937349718016 17 61410199093641216 18 1174438559356747776