login
Number of dimer tilings of a 2*n x 10 Moebius strip.
2

%I #11 May 04 2021 02:10:27

%S 1,123,34276,10894561,3625549353,1234496016491,425588878897051,

%T 147716667776449068,51459452422736225401,17962375573820654607091,

%U 6276640725138515237851803,2194525820018749279915303361,767517569389298359121889024076,268477550040900162034429991254323

%N Number of dimer tilings of a 2*n x 10 Moebius strip.

%F a(n)^2 = 4^n * Resultant(U_{2*n}(x/2), T_{10}(i*x/2))), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1).

%t a[n_] := 2^n * Sqrt[Resultant[ChebyshevU[2*n, x/2], ChebyshevT[10, I*x/2], x]]; Array[a, 14, 0] (* _Amiram Eldar_, May 04 2021 *)

%o (PARI) {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(10, 1, I*x/2)))}

%Y Column 5 of A103997.

%Y Column 10 of A334178.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Apr 17 2020