Number of permutations of length n that avoid the patterns 132, 4321.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =31a(6) =66a(7) =127a(8) =225a(9) =373a(10) =586a(11) =881a(12) =1277a(13) =1795a(14) =2458a(15) =3291a(16) =4321a(17) =5577a(18) =7090a(19) =8893a(20) =11021a(21) =13511a(22) =16402a(23) =19735a(24) =23553a(25) =27901a(26) =32826a(27) =38377a(28) =44605a(29) =51563