# A335819 (b-file synthesized from sequence entry) 0 1 1 3 2 12 3 54 4 270 5 1458 6 8424 7 51516 8 331452 9 2230740 10 15641424 11 113846472 12 857706408 13 6671592216 14 53465326560 15 440602852752 16 3727748253456 17 32332181692464 18 287111706003648 19 2607272929404000 20 24187186030419936 21 228997933855499808 22 2210786521482955392 23 21746223198911853504