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A168589
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a(n) = (2 - 3^n)*(-1)^n.
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3
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1, 1, -7, 25, -79, 241, -727, 2185, -6559, 19681, -59047, 177145, -531439, 1594321, -4782967, 14348905, -43046719, 129140161, -387420487, 1162261465, -3486784399, 10460353201, -31381059607, 94143178825, -282429536479
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OFFSET
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0,3
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COMMENTS
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A signed version of A058481 preceded by 1.
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (-4, -3).
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FORMULA
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a(n) = -4*a(n-1) - 3*a(n-2) for n > 1; a(0) = 1, a(1) = 1.
G.f.: (1 + 5*x)/((1+x)*(1+3*x)).
E.g.f.: 2*exp(-x) - exp(-3*x). - G. C. Greubel, Jul 26 2016
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MATHEMATICA
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Table[(2 - 3^n)*(-1)^n, {n, 0, 50}] (* G. C. Greubel, Jul 26 2016 *)
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PROG
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(Magma) [ (2-3^n)*(-1)^n: n in [0..25] ];
(PARI) a(n)=(2-3^n)*(-1)^n \\ Charles R Greathouse IV, Jul 26 2016
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CROSSREFS
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Cf. A058481 (3^n-2).
Sequence in context: A155281 A155254 A155295 * A058481 A220387 A155294
Adjacent sequences: A168586 A168587 A168588 * A168590 A168591 A168592
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KEYWORD
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sign,easy
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AUTHOR
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Klaus Brockhaus, Nov 30 2009
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STATUS
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approved
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