Number of permutations of length n which avoid the patterns 123, 3241.

Terms

a(0) =1a(1) =2a(2) =5a(3) =13a(4) =32a(5) =74a(6) =163a(7) =347a(8) =722a(9) =1480a(10) =3005a(11) =6065a(12) =12196a(13) =24470a(14) =49031a(15) =98167a(16) =196454a(17) =393044a(18) =786241a(19) =1572653a(20) =3145496a(21) =6291202a(22) =12582635a(23) =25165523a(24) =50331322a(25) =100662944a(26) =201326213a(27) =402652777a(28) =805305932a(29) =1610612270