Number of permutations of length n which avoid the patterns 231, 12345.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =41a(6) =116a(7) =302a(8) =715a(9) =1549a(10) =3106a(11) =5831a(12) =10352a(13) =17525a(14) =28484a(15) =44696a(16) =68021a(17) =100777a(18) =145810a(19) =206569a(20) =287186a(21) =392561a(22) =528452a(23) =701570a(24) =919679a(25) =1191701a(26) =1527826a(27) =1939627a(28) =2440180a(29) =3044189