Triangle read by rows: T(n,k) is the number of involutions of {1,2,...,n} having k descents (n >= 1; 0 <= k < n).

A161126

Triangle read by rows: T(n,k) is the number of involutions of {1,2,...,n} having k descents (n >= 1; 0 <= k < n).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =1a(6) =1a(7) =4a(8) =4a(9) =1a(10) =1a(11) =6a(12) =12a(13) =6a(14) =1a(15) =1a(16) =9a(17) =28a(18) =28a(19) =9a(20) =1a(21) =1a(22) =12a(23) =57a(24) =92a(25) =57a(26) =12a(27) =1a(28) =1a(29) =16

External references