Number of permutations which are the union of an increasing and a decreasing subsequence.

A029759

Number of permutations which are the union of an increasing and a decreasing subsequence.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =86a(6) =340a(7) =1340a(8) =5254a(9) =20518a(10) =79932a(11) =311028a(12) =1209916a(13) =4707964a(14) =18330728a(15) =71429176a(16) =278586182a(17) =1087537414a(18) =4249391468a(19) =16618640836a(20) =65048019092a(21) =254814326164a(22) =998953992728

External references