Number of permutations of [n] avoiding {1234, 1324, 2341}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =77a(6) =284a(7) =1041a(8) =3789a(9) =13730a(10) =49679a(11) =179906a(12) =653083a(13) =2378702a(14) =8696754a(15) =31921462a(16) =117624497a(17) =435047541a(18) =1614769933a(19) =6013417811a(20) =22463101851a(21) =84151166305a(22) =316084324517