# A218034 (b-file synthesized from sequence entry) 0 1 1 4 2 12 3 24 4 84 5 240 6 732 7 2184 8 6564 9 19680 10 59052 11 177144 12 531444 13 1594320 14 4782972 15 14348904 16 43046724 17 129140160 18 387420492 19 1162261464 20 3486784404 21 10460353200 22 31381059612 23 94143178824 24 282429536484 25 847288609440 26 2541865828332 27 7625597484984 28 22876792454964