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a(n) equals the (n*(n+1)/2)-th partial sum of the self-convolution cube of A010054, which has the g.f.: Sum_{k>=0} x^(k*(k+1)/2).
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%I #3 Mar 30 2012 18:36:49

%S 1,4,11,26,54,90,151,232,326,456,612,811,1030,1304,1607,1953,2383,

%T 2812,3329,3893,4515,5226,5983,6809,7703,8718,9762,10891,12160,13475,

%U 14868,16380,17986,19699,21524,23415,25482,27658,29923,32288,34814,37452

%N a(n) equals the (n*(n+1)/2)-th partial sum of the self-convolution cube of A010054, which has the g.f.: Sum_{k>=0} x^(k*(k+1)/2).

%F a(n) = [x^(n*(n+1)/2)] [Sum_{k>=0} x^(k*(k+1)/2)]^3/(1-x).

%o (PARI) {a(n)=local(X=x+x*O(x^(n*(n+1)/2))); polcoeff((eta(X^2)^2/eta(X))^3/(1-X),n*(n+1)/2)}

%Y Cf. A109413, A109415, A010054.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jun 27 2005