Number of permutations of length n which avoid the patterns 1243, 2341, 4321.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =71a(5) =204a(6) =479a(7) =951a(8) =1687a(9) =2764a(10) =4269a(11) =6299a(12) =8961a(13) =12372a(14) =16659a(15) =21959a(16) =28419a(17) =36196a(18) =45457a(19) =56379a(20) =69149a(21) =83964a(22) =101031a(23) =120567a(24) =142799a(25) =167964a(26) =196309a(27) =228091a(28) =263577a(29) =303044