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 A171371 a(n) = 6*a(n-1) + 8*a(n-2) with a(1) = 8, a(2) = 18. 1
 8, 18, 172, 1176, 8432, 60000, 427456, 3044736, 21688064, 154486272, 1100422144, 7838423040, 55833915392, 397710876672, 2832936583168, 20179306512384, 143739331739648, 1023870442536960, 7293137309138944, 51949787395129344, 370043822843887616 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Seen on a quiz. The recurrence was supplied by Zak Seidov, Dec 07 2009. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..200 Index entries for linear recurrences with constant coefficients, signature (6,8). FORMULA G.f.: 2*x*(-4 + 15*x)/(-1 + 6*x + 8*x^2). - V.J. Pohjola, Dec 07 2009 a(n) = 8*A189800(n) - 30*A189800(n-1). - R. J. Mathar, Nov 17 2011 From Franck Maminirina Ramaharo, Nov 23 2018: (Start) a(n) = ((77*sqrt(17) - 255)*(sqrt(17) + 3)^n - (77*sqrt(17) + 255)*(3 - sqrt(17))^n)/136. E.g.f.: ((77*sqrt(17)*sinh(sqrt(17)*x) - 255*cosh(sqrt(17)*x))*exp(3*x) + 255)/68. (End) MATHEMATICA a[1] = 8; a[2] = 18; a[n_] := a[n] = 6*a[n - 1] + 8*a[n - 2]; Array[a, 20] (* Amiram Eldar, Nov 23 2018 *) PROG (MAGMA) I:=[8, 18]; [n le 2 select I[n] else 6*Self(n-1)+8*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Nov 18 2011 CROSSREFS Sequence in context: A219524 A259852 A215174 * A092692 A001151 A177367 Adjacent sequences:  A171368 A171369 A171370 * A171372 A171373 A171374 KEYWORD nonn,easy AUTHOR Anonymous, Dec 06 2009 EXTENSIONS More terms from N. J. A. Sloane, Dec 07 2009 G.f. and name adapted to the offset by Bruno Berselli, Apr 04 2011 STATUS approved

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Last modified January 19 17:45 EST 2019. Contains 319309 sequences. (Running on oeis4.)