Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k entries divisible by 3 that are followed by a smaller entry (n>=1, k>=0).
A136718
Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k entries divisible by 3 that are followed by a smaller entry (n>=1, k>=0).
Terms
- a(0) =1a(1) =2a(2) =2a(3) =4a(4) =12a(5) =12a(6) =72a(7) =48a(8) =72a(9) =456a(10) =192a(11) =960a(12) =3120a(13) =960a(14) =10800a(15) =23760a(16) =5760a(17) =10800a(18) =133920a(19) =183600a(20) =34560a(21) =241920a(22) =1572480a(23) =1572480a(24) =241920a(25) =4233600a(26) =18869760a(27) =14878080a(28) =1935360a(29) =4233600
External references
- oeis: A136718