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 A308761 #43 Feb 28 2021 08:12:06
%S A308761 1956242,643041038,294554220578,152849502772958,83804387156528018,
%T A308761 47217865780262297342,26990513247252188990402,
%U A308761 15550772782091243971206638,8999393061535308152171682002,5221063878050546380074377019392
%N A308761 Number of perfect matchings in the graph C_{11} X C_{2n}.
%C A308761 This sequence satisfies a recurrence relation of order 243.
%H A308761 Seiichi Manyama, <a href="/A308761/b308761.txt">Table of n, a(n) for n = 2..361</a>
%H A308761 S. N. Perepechko, <a href="http://www.jip.ru/2016/333-361-2016.pdf">The number of perfect matchings on C_m X C_n graphs</a>, (in Russian), Information Processes, 2016, V. 16, No. 4, pp. 333-361.
%H A308761 S. N. Perepechko, <a href="https://doi.org/10.1134/S0361768819020075">Counting Near-Perfect Matchings on C_m × C_n Tori of Odd Order in the Maple System</a>, Programming and Computer Software, 45(2019), 65-72.
%H A308761 Sergey Perepechko, <a href="/A308761/a308761.pdf">Generating function</a> in Maple notation.
%F A308761 a(n) = sqrt( Product_{j=1..n} Product_{k=1..11} (4*sin((2*j-1)*Pi/(2*n))^2 + 4*sin((2*k-1)*Pi/11)^2) ). - _Seiichi Manyama_, Feb 14 2021
%o A308761 (PARI) default(realprecision, 120);
%o A308761 a(n) = round(sqrt(prod(j=1, n, prod(k=1, 11, 4*sin((2*j-1)*Pi/(2*n))^2+4*sin((2*k-1)*Pi/11)^2)))); \\ _Seiichi Manyama_, Feb 14 2021
%Y A308761 Column k=11 of A341533.
%Y A308761 Cf. A230033, A231485, A232804, A253678, A281583, A281679.
%K A308761 nonn
%O A308761 2,1
%A A308761 _Sergey Perepechko_, Jul 04 2019