Number of 123-segmented permutations of length n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =18a(5) =56a(6) =182a(7) =607a(8) =2064a(9) =7132a(10) =24970a(11) =88383a(12) =315748a(13) =1137014a(14) =4122762a(15) =15039631a(16) =55157790a(17) =203255438a(18) =752190764a(19) =2794352648a(20) =10417047964a(21) =38956725596a(22) =146108755556a(23) =549442692378