Number of permutations of length n which avoid the patterns 231, 1432, 4123.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =25a(5) =50a(6) =97a(7) =184a(8) =345a(9) =642a(10) =1189a(11) =2196a(12) =4049a(13) =7458a(14) =13729a(15) =25264a(16) =46481a(17) =85506a(18) =157285a(19) =289308a(20) =532137a(21) =978770a(22) =1800257a(23) =3311208a(24) =6090281a(25) =11201794a(26) =20603333a(27) =37895460a(28) =69700641a(29) =128199490