OFFSET
1,1
REFERENCES
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..150
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.
F. Faase, Results from the counting program
P. Raff, Spanning Trees in Grid Graphs, arXiv:0809.2551 [math.CO], 2008.
P. Raff, Analysis of the Number of Spanning Trees of C_4 x P_n. Contains sequence, recurrence, generating function, and more. [Dead link]
FORMULA
a(1) = 4,
a(2) = 384,
a(3) = 31500,
a(4) = 2558976,
a(5) = 207746836,
a(6) = 16864848000 and
a(n) = 90a(n-1) - 735a(n-2) + 1548a(n-3) - 735a(n-4) + 90a(n-5) - a(n-6).
G.f.: 4x(x^4+6x^3-30x^2+6x+1)/(x^6-90x^5+735x^4-1548x^3+735x^2-90x+1). [Paul Raff, Mar 06 2009]
a(n) = 4*A001109(n)*A098301(n). [R. K. Guy, seqfan list, Mar 28 2009] [From R. J. Mathar, Jun 03 2009]
MAPLE
a:= n-> (Matrix([[4, 0, -4, -384, -31500, -2558976]]). Matrix(6, (i, j)-> if (i=j-1) then 1 elif j=1 then [90, -735, 1548, -735, 90, -1][i] else 0 fi)^(n-1))[1, 1]; seq(a(n), n=1..20); # Alois P. Heinz, Aug 01 2008
MATHEMATICA
a[n_] := (Sqrt[2]/3)*Sinh[n*ArcCosh[3]]*Sinh[n*ArcCosh[7]/2]^2 // Round; Array[a, 20] (* Jean-François Alcover, Jan 31 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Added recurrence from Faase's web page. - N. J. A. Sloane, Feb 03 2009
STATUS
approved