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A115164
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a(n) = 2*Abs[(3/10)*(-1(-4)^n)-(2/5)*(4+(-4)^n)*UnitStep[ -1+n]].
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0
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3, 7, 9, 55, 201, 823, 3273, 13111, 52425, 209719, 838857, 3355447, 13421769, 53687095, 214748361, 858993463, 3435973833, 13743895351, 54975581385, 219902325559, 879609302217, 3518437208887, 14073748835529, 56294995342135
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OFFSET
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0,1
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LINKS
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Table of n, a(n) for n=0..23.
Index to sequences with linear recurrences with constant coefficients, signature (3,4).
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FORMULA
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a(n) = (4^(1+n)-19*(-1)^n)/5 for n>0. a(n) = 3*a(n-1)+4*a(n-2) for n>2. G.f.: (24*x^2+2*x-3)/((x+1)*(4*x-1)). [Colin Barker, Oct 31 2012]
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MATHEMATICA
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g0[n_] = 3/2 - Sum[(-1)^(i + 1)/2^(2*i + 1), {i, 0, n} f[n]=ZTransform[g0[n], n, x] g[n_] = InverseZTransform[f[1/x], x, n] a1 = Table[2*Abs[g[n]], {n, 1, 25}]
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CROSSREFS
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Sequence in context: A128052 A033681 A074339 * A003033 A193945 A087147
Adjacent sequences: A115161 A115162 A115163 * A115165 A115166 A115167
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KEYWORD
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nonn,uned,easy
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AUTHOR
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Roger Bagula, Mar 06 2006
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STATUS
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approved
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