# A020037 (b-file synthesized from sequence entry) 0 1 1 1 2 1 3 4 4 15 5 74 6 427 7 2901 8 22624 9 199095 10 1951127 11 21072175 12 248651668 13 3182741351 14 43921830648 15 650043093588 16 10270680878694 17 172547438762056 18 3071344409964594 19 57741274907334370 20 1143277243165220534