# A203715 (b-file synthesized from sequence entry) 1 1 2 3 3 6 4 34 5 120 6 1096 7 5040 8 56848 9 362880 10 5451136 11 39916800 12 688876288 13 6227020800 14 130789805056 15 1307674368000 16 29497569445888 17 355687428096000 18 9746045395173376 19 121645100408832000 20 3451902721622867968 21 51090942171709440000 22 1686006043164464644096