%I A139400
%S A139400 1,780,380160,170537640,74795194705,32565539635200,14143261515284447,
%T A139400 6136973985625588560,2662079368040434932480,1154617875754582889149500,
%U A139400 500769437567956298239402223,217185579535490113365186969600
%N A139400 Number of spanning trees in the graph P_6 x P_n.
%H A139400 P. Raff, <a href="b139400.txt">Table of n, a(n) for n=1..208</a>
%H A139400 Paul Raff, <a href="http://arxiv.org/abs/0809.2551">Spanning Trees in 
               Grid Graphs</a>, arXiv:0809.2551 [math.CO]
%F A139400 a(n) = 780 a(n - 1) - 194881 a(n - 2) + 22377420 a(n - 3) - 1419219792 
               a(n - 4) + 55284715980 a(n - 5) - 1410775106597 a(n - 6) + 24574215822780 
               a(n - 7) - 300429297446885 a(n - 8) + 2629946465331120 a(n - 9) - 
               16741727755133760 a(n - 10)
%F A139400 + 78475174345180080 a(n - 11) - 273689714665707178 a(n - 12) + 716370537293731320 
               a(n - 13) - 1417056251105102122 a(n - 14) + 2129255507292156360 a(n 
               - 15) - 2437932520099475424 a(n - 16) + 2129255507292156360 a(n - 
               17)
%F A139400 - 1417056251105102122 a(n - 18) + 716370537293731320 a(n - 19) - 273689714665707178 
               a(n - 20) + 78475174345180080 a(n - 21) - 16741727755133760 a(n - 
               22) + 2629946465331120 a(n - 23) - 300429297446885 a(n - 24) + 24574215822780 
               a(n - 25) - 1410775106597 a(n - 26) + 55284715980 a(n - 27) - 1419219792 
               a(n - 28) + 22377420 a(n - 29) - 194881 a(n - 30) + 780 a(n - 31) 
               - a(n - 32)
%e A139400 a(2) = 780, as can be verified from the seventh entry of A001353, which 
               corresponds to the number of spanning trees of the same graph.
%Y A139400 Sequence in context: A008746 A147547 A135198 this_sequence A115467 A020231 
               A038477
%Y A139400 Adjacent sequences: A139397 A139398 A139399 this_sequence A139401 A139402 
               A139403
%K A139400 easy,nonn
%O A139400 1,2
%A A139400 Paul Raff (praff(AT)math.rutgers.edu), Jun 09 2008; corrected recurrence 
               Feb 03 2009