Number of 4-ascent sequences of length n that avoid the pattern 00.

Terms

a(0) =1a(1) =1a(2) =4a(3) =16a(4) =58a(5) =190a(6) =564a(7) =1526a(8) =3794a(9) =8747a(10) =18869a(11) =38402a(12) =74273a(13) =137372a(14) =244271a(15) =419488a(16) =698415a(17) =1131045a(18) =1786650a(19) =2759580a(20) =4176372a(21) =6204378a(22) =9062142a(23) =13031778a(24) =18473624a(25) =25843471a(26) =35712691a(27) =48791614a(28) =65956531a(29) =88280728