OFFSET
1,3
COMMENTS
FORMULA
u(n,x) = u(n-1,x) + (x+1)*v(n-1,x),
v(n,x) = (x+1)*u(n-1,x) + x*v(n-1,x),
where u(1,x)=1, v(1,x)=1.
From Philippe Deléham, Apr 11 2012: (Start)
T(n,k) = A185081(n,k+1).
T(n,k) = T(n-1,k) + T(n-1,k-1) + T(n-2,k) + T(n-2,k-1) + T(n-2,k-2), T(1,0) = T(2,0) = 1, T(2,1) = 2 and T(n,k) = 0 if k < 0 or if k >= n. (End)
EXAMPLE
First five rows:
1;
1, 2;
2, 4, 3;
3, 9, 10, 5;
5, 18, 28, 22, 8;
First three polynomials v(n,x): 1, 1 + 2x, 2 + 4x + 3x^2.
From Philippe Deléham, Apr 11 2012: (Start)
Triangle in A185081 begins:
1;
0, 1;
0, 1, 2;
0, 2, 4, 3;
0, 3, 9, 10, 5;
0, 5, 18, 28, 22, 8;
... (End)
MATHEMATICA
u[1, x_] := 1; v[1, x_] := 1; z = 16;
u[n_, x_] := u[n - 1, x] + (x + 1)*v[n - 1, x];
v[n_, x_] := (x + 1)*u[n - 1, x] + x*v[n - 1, x];
Table[Expand[u[n, x]], {n, 1, z/2}]
Table[Expand[v[n, x]], {n, 1, z/2}]
cu = Table[CoefficientList[u[n, x], x], {n, 1, z}];
TableForm[cu]
Flatten[%] (* A209137 *)
Table[Expand[v[n, x]], {n, 1, z}]
cv = Table[CoefficientList[v[n, x], x], {n, 1, z}];
TableForm[cv]
Flatten[%] (* A209138 *)
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Clark Kimberling, Mar 05 2012
STATUS
approved