# A091321 (b-file synthesized from sequence entry) 1 1 2 6 3 28 4 90 5 120 6 496 7 672 8 8128 9 10080 10 63700 11 220500 12 523776 13 1323000 14 1528800 15 2056320 16 7856640 17 33550336 18 44553600 19 162729000 20 252927360 21 459818240 22 1379454720 23 1476304896 24 1980840960 25 8589869056