OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Spanning Tree
Eric Weisstein's World of Mathematics, Torus Grid Graph
PROG
(PARI) default(realprecision, 120);
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)));
a(n) = T(9, n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Dec 02 2022
STATUS
approved