Number of permutations of length n which avoid the patterns 132, 3421, 4231.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =26a(5) =52a(6) =99a(7) =184a(8) =340a(9) =632a(10) =1189a(11) =2268a(12) =4382a(13) =8556a(14) =16839a(15) =33328a(16) =66216a(17) =131888a(18) =263113a(19) =525428a(20) =1049906a(21) =2098692a(22) =4196075a(23) =8390632a(24) =16779516a(25) =33557032a(26) =67111789a(27) =134221004a(28) =268439110a(29) =536874972