# A012709 (b-file synthesized from sequence entry) 0 1 1 1 2 3 3 12 4 57 5 340 6 2305 7 18186 8 158977 9 1560840 10 16695553 11 196272142 12 2483596577 13 34036624700 14 497515462561 15 7792454528002 16 129248702613505 17 2278494692749840 18 42291311707716609 19 828953188249846678