Number of permutations of length n which avoid the patterns 2341, 4312.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =86a(6) =338a(7) =1318a(8) =5110a(9) =19770a(10) =76466a(11) =295810a(12) =1144530a(13) =4428622a(14) =17136186a(15) =66306722a(16) =256565926a(17) =992749334a(18) =3841316550a(19) =14863484902a(20) =57512368162a(21) =222536820262a(22) =861078033110