# A134295 (b-file synthesized from sequence entry) 1 2 2 2 3 6 4 16 5 65 6 312 7 1813 8 12288 9 95617 10 840960 11 8254081 12 89441280 13 1060369921 14 13649610240 15 189550368001 16 2824077312000 17 44927447040001 18 760034451456000 19 13622700994560001 20 257872110354432000 21 5140559166898176001