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A155155
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a(n) = 2*(10*3^n - 1).
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1
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18, 58, 178, 538, 1618, 4858, 14578, 43738, 131218, 393658, 1180978, 3542938, 10628818, 31886458, 95659378, 286978138, 860934418, 2582803258, 7748409778, 23245229338, 69735688018, 209207064058, 627621192178, 1882863576538
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 4*a(n-1) - 3*a(n-2).
G.f.: ( 18 - 14*x ) / ( (1-x)*(1-3*x) ).
a(n) = 3*a(n-1) - a(n-2) + 3*a(n-3) + 8.
E.g.f.: 2*( 10*exp(3*x) - exp(x) ). (End)
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MAPLE
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MATHEMATICA
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PROG
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(Sage) [2*(10*3^n - 1) for n in (0..30)] # G. C. Greubel, Mar 20 2021
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CROSSREFS
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KEYWORD
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nonn,easy,less
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AUTHOR
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STATUS
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approved
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