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 A114479 Kekulé numbers for certain benzenoids. 1
 3, 20, 136, 928, 6336, 43264, 295424, 2017280, 13774848, 94060544, 642285568, 4385800192, 29948116992, 204498534400, 1396403339264, 9535238438912, 65110680797184, 444603538866176, 3035942864551936, 20730714605486080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 205). LINKS Index entries for linear recurrences with constant coefficients, signature (8,-8). FORMULA a(n) = ((4+sqrt(8))^(n+1) + (4-sqrt(8))^(n+1))/16. a(n) = 8*a(n-1) - 8*a(n-2). - Colin Barker, Aug 30 2013 G.f.: -x*(4*x-3) / (8*x^2 - 8*x + 1). - Colin Barker, Aug 30 2013 a(n)= 3*A057084(n-1) - 4*A057084(n-2). - R. J. Mathar, Aug 30 2013 MAPLE a:=((4+sqrt(8))^(n+1)+(4-sqrt(8))^(n+1))/16: seq(expand(a(n)), n=1..23); CROSSREFS Sequence in context: A216778 A056306 A056298 * A074574 A267899 A073514 Adjacent sequences:  A114476 A114477 A114478 * A114480 A114481 A114482 KEYWORD nonn,easy AUTHOR Emeric Deutsch, Nov 30 2005 STATUS approved

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Last modified February 18 02:57 EST 2020. Contains 332006 sequences. (Running on oeis4.)