Number of ascent sequences avoiding the pattern 201.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =52a(6) =201a(7) =843a(8) =3764a(9) =17659a(10) =86245a(11) =435492a(12) =2261769a(13) =12033165a(14) =65369590a(15) =361661809a(16) =2033429427a(17) =11597912588a(18) =67004252081a(19) =391599609911