# A177281 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 6 4 24 5 120 6 720 7 5040 8 40320 9 362880 10 3628800 11 32659200 12 267805440 13 2033498880 14 14563332000 15 100185340320 16 672903217200 17 4472291398032 18 29721557854116 19 199059839989844