Number of permutations of [n] avoiding {4231, 2143, 1342}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =71a(6) =218a(7) =614a(8) =1619a(9) =4065a(10) =9840a(11) =23168a(12) =53393a(13) =120995a(14) =270518a(15) =598218a(16) =1310943a(17) =2851061a(18) =6160652a(19) =13238564a(20) =28311869a(21) =60293463a(22) =127926642a(23) =270533006a(24) =570425771a(25) =1199571401a(26) =2516582888a(27) =5268046344a(28) =11005854249a(29) =22951232075