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 A123358 Kekulé numbers for certain benzenoids (see the Cyvin-Gutman book for details). 2
 1, 10, 125, 1625, 21250, 278125, 3640625, 47656250, 623828125, 8166015625, 106894531250, 1399267578125, 18316650390625, 239768066406250, 3138604736328125, 41084869384765625, 537807922363281250, 7039997100830078125, 92154758453369140625, 1206321449279785156250, 15790952777862548828125, 206706255435943603515625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 210, formula page 204). Index entries for linear recurrences with constant coefficients, signature (15,-25). FORMULA G.f.: -(5*x-1) / (25*x^2-15*x+1). - Colin Barker, Aug 29 2013 a(n)=5^n*A001519(n+1). - R. J. Mathar, Jul 26 2019 MAPLE A123358 := proc(n)     option remember;     if n <= 1 then         op(n+1, [1, 10]) ;     else         15*procname(n-1)-25*procname(n-2) ;     end if end proc: seq( A123358(n), n=0..30) ; # R. J. Mathar, Jul 26 2019 CROSSREFS Sequence in context: A005174 A034668 A215854 * A230390 A089832 A161170 Adjacent sequences:  A123355 A123356 A123357 * A123359 A123360 A123361 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Oct 10 2006 STATUS approved

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Last modified January 23 04:16 EST 2020. Contains 331168 sequences. (Running on oeis4.)