a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 267) or the same sequence for the mesh pattern (12, 417).

A289594

a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 267) or the same sequence for the mesh pattern (12, 417).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =16a(6) =63a(7) =239a(8) =880a(9) =3184a(10) =11431a(11) =40976a(12) =147189a(13) =530804a(14) =1923361a(15) =7004035a(16) =25630072a(17) =94221600a(18) =347862855a(19) =1289362364a(20) =4796332961a(21) =17901098044a(22) =67014199489a(23) =251572855728a(24) =946836145089

External references