# A072335 (b-file synthesized from sequence entry) 0 1 1 4 2 16 3 60 4 225 5 840 6 3136 7 11704 8 43681 9 163020 10 608400 11 2270580 12 8473921 13 31625104 14 118026496 15 440480880 16 1643897025 17 6135107220 18 22896531856 19 85451020204 20 318907548961 21 1190179175640 22 4441809153600 23 16577057438760 24 61866420601441 25 230888624967004