Number of length n inversion sequences avoiding the patterns 000 and 102.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =40a(6) =121a(7) =373a(8) =1181a(9) =3796a(10) =12391a(11) =40902a(12) =136408a(13) =458735a(14) =1554220a(15) =5299505a(16) =18172874a(17) =62630809a(18) =216821747a(19) =753646690a(20) =2629153881a(21) =9202404515a(22) =32307100270a(23) =113735363082a(24) =401418269205