Number of permutations of length n which avoid the patterns 1234, 2341, 4132.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =72a(5) =221a(6) =605a(7) =1517a(8) =3574a(9) =8065a(10) =17671a(11) =37953a(12) =80424a(13) =168885a(14) =352481a(15) =732581a(16) =1518074a(17) =3139033a(18) =6480187a(19) =13360153a(20) =27514476a(21) =56610861a(22) =116377941a(23) =239059421a(24) =490715582a(25) =1006612721a(26) =2063574895a(27) =4227833137a(28) =8657015344a(29) =17716708965