# A013315 (b-file synthesized from sequence entry) 1 0 2 1 3 2 4 2 5 12 6 72 7 272 8 968 9 5488 10 36144 11 204512 12 1135840 13 7577856 14 56287168 15 406104064 16 2933384704 17 23084016896 18 194919700480 19 1664627753984 20 14417113925632 21 131148402111488 22 1251412558922752 23 12211894620549120