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Triangle defined by g.f.: Sum_{n>=0} (4*n)!/n!^4 * x^(2*n)*y^n/(1-x-x*y)^(4*n+1), read by rows.
3

%I #9 Mar 30 2012 18:37:23

%S 1,1,1,1,26,1,1,123,123,1,1,364,3246,364,1,1,845,25210,25210,845,1,1,

%T 1686,120135,606500,120135,1686,1,1,3031,430941,6082475,6082475,

%U 430941,3031,1,1,5048,1277668,38698856,137915470,38698856,1277668,5048,1,1,7929

%N Triangle defined by g.f.: Sum_{n>=0} (4*n)!/n!^4 * x^(2*n)*y^n/(1-x-x*y)^(4*n+1), read by rows.

%C Compare the g.f. of this triangle with the g.f.s of triangles:

%C * A008459: Sum_{n>=0} (2n)!/n!^2 * x^(2n)*y^n/(1-x-xy)^(2n+1),

%C * A181543: Sum_{n>=0} (3n)!/n!^3 * x^(2n)*y^n/(1-x-xy)^(3n+1),

%C which have terms A008459(n,k) = C(n,k)^2 and A181543(n,k) = C(n,k)^3.

%e G.f.: A(x,y) = 1/(1-x-xy) + 4!*x^2*y/(1-x-xy)^5 + (8!/2!^4)*x^4*y^2/(1-x-xy)^9 + (12!/3!^4)*x^6*y^3/(1-x-xy)^13 +...

%e Triangle begins:

%e 1;

%e 1, 1;

%e 1, 26, 1;

%e 1, 123, 123, 1;

%e 1, 364, 3246, 364, 1;

%e 1, 845, 25210, 25210, 845, 1;

%e 1, 1686, 120135, 606500, 120135, 1686, 1;

%e 1, 3031, 430941, 6082475, 6082475, 430941, 3031, 1;

%e 1, 5048, 1277668, 38698856, 137915470, 38698856, 1277668, 5048, 1; ...

%o (PARI) {T(n,k)=polcoeff(polcoeff(sum(m=0,n,(4*m)!/m!^4*x^(2*m)*y^m/(1-x-x*y+x*O(x^n))^(4*m+1)),n,x),k,y)}

%Y Cf. A183066 (column 1), A183067 (row sums), A183068 (central terms).

%K tabl,sign

%O 0,5

%A _Paul D. Hanna_, Dec 22 2010