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A014989
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a(n) = (1 - (-7)^n)/8.
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13
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1, -6, 43, -300, 2101, -14706, 102943, -720600, 5044201, -35309406, 247165843, -1730160900, 12111126301, -84777884106, 593445188743, -4154116321200, 29078814248401, -203551699738806, 1424861898171643, -9974033287201500
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OFFSET
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1,2
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COMMENTS
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q-integers for q = -7.
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LINKS
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FORMULA
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a(n) = a(n-1) + q^(n-1) = (q^n - 1) / (q - 1).
G.f.: x/((1-x)*(1+7*x)).
E.g.f.: (exp(x) - exp(-7*x))/8. (End)
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MAPLE
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a:=n->sum ((-7)^j, j=0..n): seq(a(n), n=0..25); # Zerinvary Lajos, Dec 16 2008
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MATHEMATICA
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PROG
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(Sage) [gaussian_binomial(n, 1, -7) for n in range(1, 21)] # Zerinvary Lajos, May 28 2009
(Magma) I:=[1, -6]; [n le 2 select I[n] else -6*Self(n-1)+7*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Oct 22 2012
(PARI) x='x+O('x^30); Vec(x/((1-x)*(1+7*x))) \\ G. C. Greubel, May 26 2018
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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