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%I #20 May 04 2021 02:13:30
%S 1,2911,4768673,7022359583,10021992194369,14143261515284447,
%T 19872369301840986112,27873182693625548898079,
%U 39067130344394503972142977,54740416599810921320592441119,76692291658239649098972455530913,107441842254735898225957962027174559,150517199699838971875005120330439121217
%N Number of spanning trees in the graph P_7 x P_n.
%H Seiichi Manyama, <a href="/A334002/b334002.txt">Table of n, a(n) for n = 1..200</a>
%H Vaclav Kotesovec, <a href="/A334002/a334002.txt">Generating function</a>
%t a[n_] := Resultant[ChebyshevU[n - 1, x/2], ChebyshevU[6, (4 - x)/2], x]; Array[a, 13] (* _Amiram Eldar_, May 04 2021 *)
%o (Python)
%o # Using graphillion
%o from graphillion import GraphSet
%o import graphillion.tutorial as tl
%o def A116469(n, k):
%o if n == 1 or k == 1: return 1
%o universe = tl.grid(n - 1, k - 1)
%o GraphSet.set_universe(universe)
%o spanning_trees = GraphSet.trees(is_spanning=True)
%o return spanning_trees.len()
%o def A334002(n):
%o return A116469(n, 7)
%o print([A334002(n) for n in range(1, 15)])
%Y Row m=7 of A116469.
%K nonn
%O 1,2
%A _Seiichi Manyama_, Apr 12 2020
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