Triangle read by rows: T(n,k) is the number of fixed-point-free involutions of {1,2,...,2n} having k cycles with entries of opposite parities (0 <= k <= n).
A161119
Triangle read by rows: T(n,k) is the number of fixed-point-free involutions of {1,2,...,2n} having k cycles with entries of opposite parities (0 <= k <= n).
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =0a(5) =2a(6) =0a(7) =9a(8) =0a(9) =6a(10) =9a(11) =0a(12) =72a(13) =0a(14) =24a(15) =0a(16) =225a(17) =0a(18) =600a(19) =0a(20) =120a(21) =225a(22) =0a(23) =4050a(24) =0a(25) =5400a(26) =0a(27) =720a(28) =0a(29) =11025
External references
- oeis: A161119