a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 427).

A289600

a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 427).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =2a(4) =9a(5) =33a(6) =113a(7) =381a(8) =1291a(9) =4425a(10) =15357a(11) =53914a(12) =191205a(13) =684102a(14) =2466415a(15) =8951931a(16) =32683215a(17) =119949929a(18) =442281013a(19) =1637618382a(20) =6086481701a(21) =22699003810a(22) =84918443199a(23) =318593346608

External references