Number of permutations of length n which avoid the patterns 231, 12354.

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =41a(5) =119a(6) =334a(7) =902a(8) =2351a(9) =5945a(10) =14660a(11) =35408a(12) =84061a(13) =196715a(14) =454778a(15) =1040522a(16) =2359451a(17) =5308589a(18) =11862208a(19) =26345684a(20) =58196201a(21) =127926527a(22) =279970070a(23) =610271534a(24) =1325400391a(25) =2868904289a(26) =6190793084a(27) =13321109912a(28) =28588376501a(29) =61203284435