# A113990 (b-file synthesized from sequence entry) 0 1 1 4 2 12 3 36 4 116 5 416 6 1680 7 7656 8 39256 9 225348 10 1439868 11 10179116 12 79153484 13 673262240 14 6231517920 15 62461031920 16 675005395152 17 7832909636740 18 97238472215564 19 1286967352638292 20 18102901048062404 21 269852768731391808