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A221904
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a(n) = 9^n + 10^n.
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1
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2, 19, 181, 1729, 16561, 159049, 1531441, 14782969, 143046721, 1387420489, 13486784401, 131381059609, 1282429536481, 12541865828329, 122876792454961, 1205891132094649, 11853020188851841
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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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G.f.: 1/(1 - 9*x) + 1/(1 - 10*x).
E.g.f.: exp(9*x) + exp(10*x).
a(n) = 19*a(n-1) - 90*a(n-2), a(1)=2, a(2)=19.
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MATHEMATICA
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CoefficientList[Series[1/(1-9*x) + 1/(1-10*x), {x, 0, 30}], x]
LinearRecurrence[{19, -90}, {2, 19}, 30] (* Harvey P. Dale, Nov 10 2017 *)
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PROG
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(Magma) [9^n + 10^n: n in [0..30]];
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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