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%I #6 Aug 17 2021 02:48:44
%S 1,9,51,209,696,1980,5000,11475,24375,48545,91581,164934,285376,
%T 476784,772416,1217610,1873125,2819025,4159375,6027615,8592936,
%U 12067484,16714776,22859109,30896411,41306265,54665625,71663900
%N Column 4 of triangle A055898.
%H A. J. Guttmann, <a href="https://doi.org/10.1016/S0012-365X(99)00262-9">Indicators of solvability for lattice models</a>, Discrete Math., 217 (2000), 167-189 (H_4 for square lattices of Section 6).
%F G.f.: x^4*(1+3x+9x^2+9x^3+9x^4+3x^5+x^6)/((1-x)^9*(1+x)^3).
%Y Cf. A055898.
%K nonn
%O 4,2
%A _Christian G. Bower_, Jun 13 2000
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