# A355989 (b-file synthesized from sequence entry) 2 1 3 3 4 6 5 30 6 60 7 420 8 840 9 7560 10 15120 11 166320 12 332640 13 4324320 14 8648640 15 129729600 16 259459200 17 4410806400 18 8821612800 19 167610643200 20 335221286400 21 7039647014400 22 14079294028800 23 323823762662400 24 647647525324800 25 16191188133120000 26 32382376266240000