A114176 Triangle, read by rows, where the g.f. of column n, C_n(x), equals the g.f. of row n, R_n(x), divided by (1-x)^(n+1)*(1-x^2)^n, for n>=0; e.g., C_n(x) = R_n(x)/(1-x)^(n+1)/(1-x^2)^n.
1, 1, 1, 1, 3, 1, 1, 6, 6, 1, 1, 10, 18, 10, 1, 1, 15, 43, 43, 15, 1, 1, 21, 86, 135, 87, 21, 1, 1, 28, 156, 345, 345, 159, 28, 1, 1, 36, 260, 771, 1083, 777, 267, 36, 1, 1, 45, 410, 1557, 2901, 2927, 1577, 423, 45, 1, 1, 55, 615, 2913, 6909, 9219, 7001, 2973, 637, 55, 1
Offset: 0
Examples
Triangle begins: 1; 1,1; 1,3,1; 1,6,6,1; 1,10,18,10,1; 1,15,43,43,15,1; 1,21,86,135,87,21,1; 1,28,156,345,345,159,28,1; 1,36,260,771,1083,777,267,36,1; 1,45,410,1557,2901,2927,1577,423,45,1; 1,55,615,2913,6909,9219,7001,2973,637,55,1; ... where g.f. for columns is formed from g.f. of rows: column 2: (1 + 3*x + 1*x^2)/(1-x)^3/(1-x^2)^2 = 1 + 6*x + 18*x^2 + 43*x^3 + 86*x^4 + 156*x^5 +... column 3: (1 + 6*x + 6*x^2 + 1*x^3)/(1-x)^4/(1-x^2)^3 = 1 + 10*x + 43*x^2 + 135*x^3 + 345*x^4 + 771*x^5 +... column 4: (1 + 10*x + 18*x^2 + 10*x^3 + 1*x^4)/(1-x)^5/(1-x^2)^4 = 1 + 15*x + 87*x^2 + 345*x^3 + 1083*x^4 + 2901*x^5 +...
Programs
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PARI
T(n,k)=if(n
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PARI
{T(n,k)=if(n==k,1,sum(j=0,k,T(k,j)*sum(i=0,n-j-k, (-1)^(n-i-j-k)*binomial(2*k+i,i)*binomial(n-i-j-1,n-i-j-k))))} \\ Paul D. Hanna, Jun 21 2006
Formula
T(n,k) = Sum_{j=0..k} T(k,j)*Sum_{i=0..n-j-k} (-1)^(n-i-j-k)*C(2k+i,i)*C(n-i-j-1,n-i-j-k) for n>k with T(n,n)=1 for n>=0. - Paul D. Hanna, Jun 21 2006