Number of permutations in S_n avoiding 21{bar 3}54 (i.e., every occurrence of 2154 is contained in an occurrence of a 21354).

A117106

Number of permutations in S_n avoiding 21{bar 3}54 (i.e., every occurrence of 2154 is contained in an occurrence of a 21354).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =23a(5) =104a(6) =530a(7) =2958a(8) =17734a(9) =112657a(10) =750726a(11) =5207910a(12) =37387881a(13) =276467208a(14) =2097763554a(15) =16282567502a(16) =128951419810

External references