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%I #9 Nov 24 2018 01:32:16
%S -1,3,11,107,759,6039,47403,381051,3088487,25298123,208803891,
%T 1735293647,14504709959,121852053543,1028165819931,8709157908891,
%U 74025669921687,631136066733099,5395888228066083,46247311947563667,397277334830158479,3419779401039536703,29493315403546699971
%N Coefficients in an expansion of the trace of the log of the adjacency operator on the infinite grid Z x Z.
%H Bryan Clair, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v21i2p16">The Ihara zeta function of the infinite grid</a>, Electron. J. Combin., 21(2) (2014), #P2.16.
%F a(n) = Sum_{k=0..n} n*(-3)^(n-k)*(n+k)^(-1)*binomial(n+k, 2*k)*binomial(2*k, k)^2). - _Michel Marcus_, Nov 23 2018
%p f:=n->add( n*(-3)^(n-k)*(n+k)^(-1)*binomial(n+k,2*k)*binomial(2*k,k)^2, k=0..n);
%p [seq(f(n),n=1..30)];
%o (PARI) a(n) = sum(k=0, n, n*(-3)^(n-k)*(n+k)^(-1)*binomial(n+k, 2*k)*binomial(2*k, k)^2); \\ _Michel Marcus_, Nov 23 2018
%K sign
%O 1,2
%A _N. J. A. Sloane_, May 12 2014
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