# A137958 (b-file synthesized from sequence entry) 0 1 1 1 2 4 3 18 4 100 5 587 6 3660 7 23640 8 157076 9 1066281 10 7363620 11 51568732 12 365369868 13 2614235293 14 18862816112 15 137096744232 16 1002785827620 17 7376023180645 18 54525165453672 19 404858512190316 20 3018190533410664 21 22581907465905018