Triangle read by rows: T(n,k) is the number of alternating (i.e., down-up) permutations of {1,2,...,n} having k fixed points (n >= 0, 0 <= k <= ceiling(n/2)).
A162979
Triangle read by rows: T(n,k) is the number of alternating (i.e., down-up) permutations of {1,2,...,n} having k fixed points (n >= 0, 0 <= k <= ceiling(n/2)).
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =0a(5) =1a(6) =1a(7) =0a(8) =2a(9) =2a(10) =1a(11) =6a(12) =6a(13) =3a(14) =1a(15) =24a(16) =24a(17) =11a(18) =2a(19) =102a(20) =102a(21) =51a(22) =15a(23) =2a(24) =528a(25) =528a(26) =252a(27) =68a(28) =9a(29) =2952
External references
- oeis: A162979