A210637 Triangle T(n,k), read by rows, given by (2, 1/2, -1/2, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (2, -1/2, -1/2, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938.

1, 2, 2, 5, 8, 3, 12, 27, 20, 5, 29, 84, 91, 44, 8, 70, 248, 352, 251, 90, 13, 169, 708, 1240, 1164, 618, 176, 21, 408, 1973, 4106, 4771, 3344, 1414, 334, 34, 985, 5400, 13010, 18000, 15645, 8748, 3073, 620, 55

Offset: 0

Author

Philippe Deléham, Mar 26 2012

Keywords

• easy
• nonn
• tabl

Comments

Row sums are powers of 4 (A000302).

Examples

			Triangle begins :
1
2, 2
5, 8, 3
12, 27, 20, 5
29, 84, 91, 44, 8
70, 248, 352, 251, 90, 13
169, 708, 1240, 1164, 618, 176, 21
408, 1973, 4106, 4771, 3344, 1414, 334, 34
985, 5400, 13010, 18000, 15645, 8748, 3073, 620, 55
2378, 14574, 39880, 63966, 66282, 46014, 21400, 6429, 1132, 89
5741, 38896, 119129, 217232, 261185, 216348, 125028, 49772, 13061, 2040, 144
		

Crossrefs

Cf. A000045, A000129, A000302, A261056 (2nd column).

Formula

G.f.: (1+y*x)/(1-(y+2)*x-(y+1)^2*x^2).

T(n,k) = 2*T(n-1,k) + T(n-1,k-1) + T(n-2,k) + 2*T(n-2,k-1) + T(n-2,k-2), T(0,0) = 1, T(1,0) = T(1,1) = 2 and T(n,k) = 0 if k<0 or if k>n.

Sum_{k, 0<=k<=n} T(n,k)*x^k = (-1)^n*A159612(n+1), (-1)^n*A000034(n), A000007(n), A000129(n+1), A000302(n) for x = -3, -2, -1, 0, 1 respectively.

T(n,0) = A000129(n+1), T(n,n) = A000045(n+2), T(n+1,n) = 2*A004798(n+1).