A358814 - OEIS

%I #8 Feb 16 2025 08:34:04

%S 9,34928082,5312031978672,344499209234302500,16463182598208445194045,

%T 687776414074843514847584256,26818349084747196820449212376063,

%U 1005049441217682470864686231147005000,36735015407753190053984060991247792275456

%N Number of spanning trees in C_9 X C_n.

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SpanningTree.html">Spanning Tree</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TorusGridGraph.html">Torus Grid Graph</a>

%o (PARI) default(realprecision, 120);

%o T(n, k) = round(n*k*prod(a=1, n-1, prod(b=1, k-1, 4*sin(a*Pi/n)^2+4*sin(b*Pi/k)^2)));

%o a(n) = T(9, n);

%Y Row 9 of A212796.

%K nonn,changed

%O 1,1

%A _Seiichi Manyama_, Dec 02 2022