This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A103998 #12 Jul 31 2015 17:27:07
%S A103998 1,11,71,539,4271,34276,276119,2226851,17965151,144948419,1169523076,
%T A103998 9436433171,76139155439,614339685971,4956888901511,39995380044004,
%U A103998 322708555336511,2603821045832171,21009309912323639
%N A103998 Number of dimer tilings of a 4 x 2n Moebius strip.
%H A103998 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (11, -25, 11, -1).
%F A103998 G.f.: (1-25x^2+22x^3-3x^4)/(1-11x+25x^2-11x^3+x^4).
%F A103998 a(0)=1, a(1)=11, a(2)=71, a(3)=539, a(4)=4271, a(n)=11*a(n-1)-25*a(n-2)+ 11*a(n-3)-a(n-4). - _Harvey P. Dale_, Jun 15 2011
%t A103998 Join[{1},LinearRecurrence[{11,-25,11,-1},{11,71,539,4271},40]] (* or *) CoefficientList[ Series[ (1-25x^2+22x^3-3x^4)/ (1-11x+ 25x^2- 11x^3+x^4),{x,0,40}],x] (* _Harvey P. Dale_, Jun 15 2011 *)
%Y A103998 Cf. Second row of array A103997.
%K A103998 nonn
%O A103998 0,2
%A A103998 _Ralf Stephan_, Feb 26 2005