Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k even entries that are followed by a smaller entry (n>=0, k>=0).
A134434
Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k even entries that are followed by a smaller entry (n>=0, k>=0).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =2a(6) =4a(7) =16a(8) =4a(9) =36a(10) =72a(11) =12a(12) =36a(13) =324a(14) =324a(15) =36a(16) =576a(17) =2592a(18) =1728a(19) =144a(20) =576a(21) =9216a(22) =20736a(23) =9216a(24) =576a(25) =14400a(26) =115200a(27) =172800a(28) =57600a(29) =2880
External references
- oeis: A134434