# A003756 (b-file synthesized from sequence entry) 1 1 2 0 3 24 4 54 5 492 6 1944 7 11976 8 57024 9 313440 10 1587168 11 8417472 12 43483392 13 227995008 14 1185394176 15 6192642048 16 32263570944 17 168350991360 18 877689686016 19 4578049517568 20 23872537976832 21 124504626978816 22 649282059657216 23 3386128302882816 24 17658788068196352