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 A090728 a(n) = 20a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 20. 2
 2, 20, 398, 7940, 158402, 3160100, 63043598, 1257711860, 25091193602, 500566160180, 9986232009998, 199224074039780, 3974495248785602, 79290680901672260, 1581839122784659598, 31557491774791519700, 629567996373045734402, 12559802435686123168340 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Except for the first term, positive values of x (or y) satisfying x^2 - 20xy + y^2 + 396 = 0. - Colin Barker, Feb 28 2014 LINKS Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (20,-1). FORMULA a(n) = p^n + q^n, where p = 10 + 3sqrt(11) and q = 10 - 3sqrt(11). - Tanya Khovanova, Feb 06 2007 G.f.: (2-20*x)/(1-20*x+x^2). [From Philippe Deléham, Nov 02 2008] MATHEMATICA a[0] = 2; a[1] = 20; a[n_] := 20a[n - 1] - a[n - 2]; Table[ a[n], {n, 0, 15}] (* Robert G. Wilson v, Jan 30 2004 *) PROG (Sage) [lucas_number2(n, 20, 1) for n in xrange(0, 20)] - Zerinvary Lajos, Jun 27 2008 (PARI) Vec((2-20*x)/(1-20*x+x^2) + O(x^100)) \\ Colin Barker, Feb 28 2014 CROSSREFS Cf. A080959, A037035, A054877. Cf. A001085. Sequence in context: A218306 A009236 A078698 * A210896 A090309 A002116 Adjacent sequences:  A090725 A090726 A090727 * A090729 A090730 A090731 KEYWORD easy,nonn AUTHOR Nikolay V. Kosinov (kosinov(AT)unitron.com.ua), Jan 18 2004 EXTENSIONS More terms from Robert G. Wilson v, Jan 30 2004 More terms from Colin Barker, Feb 28 2014 STATUS approved

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Last modified December 18 08:16 EST 2018. Contains 318219 sequences. (Running on oeis4.)