4796595087

Appears in sequences

• a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 271) or the same sequence for the mesh patterns (12, 303), (12, 331), (12, 421), (12, 423), (12, 459), (12, 481), (12, 489).at n=20A289597