# A002903 (b-file synthesized from sequence entry) 0 1 1 4 2 28 3 196 4 1324 5 8980 6 60028 7 402412 8 2675860 9 17826340 10 118145548 11 784024780 12 5184334996 13 34313323804 14 226516271020 15 1496391824212 16 9865667928796 17 65080520041804 18 428641139406628 19 2824446024265444 20 18587519784608836 21 122369125319060884