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 A308761 Number of perfect matchings in the graph C_{11} X C_{2n}. 5
 1956242, 643041038, 294554220578, 152849502772958, 83804387156528018, 47217865780262297342, 26990513247252188990402, 15550772782091243971206638, 8999393061535308152171682002, 5221063878050546380074377019392 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS This sequence satisfies a recurrence relation of order 243. LINKS Seiichi Manyama, Table of n, a(n) for n = 2..361 S. N. Perepechko, The number of perfect matchings on C_m X C_n graphs, (in Russian), Information Processes, 2016, V. 16, No. 4, pp. 333-361. S. N. Perepechko, Counting Near-Perfect Matchings on C_m × C_n Tori of Odd Order in the Maple System, Programming and Computer Software, 45(2019), 65-72. Sergey Perepechko, Generating function in Maple notation. FORMULA 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 PROG (PARI) default(realprecision, 120); 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 CROSSREFS Column k=11 of A341533. Cf. A230033, A231485, A232804, A253678, A281583, A281679. Sequence in context: A017337 A017457 A017589 * A236910 A251961 A067454 Adjacent sequences: A308758 A308759 A308760 * A308762 A308763 A308764 KEYWORD nonn AUTHOR Sergey Perepechko, Jul 04 2019 STATUS approved

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Last modified May 29 04:03 EDT 2023. Contains 363029 sequences. (Running on oeis4.)