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A081625
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a(n) = 2*5^n - 3^n.
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6
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1, 7, 41, 223, 1169, 6007, 30521, 154063, 774689, 3886567, 19472201, 97479103, 487749809, 2439811927, 12202248281, 61020807343, 305132734529, 1525749766087, 7629007110761, 38145810394783, 190731376496849
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = 8*a(n-1) - 15*a(n-2), a(0)=1, a(1)=7.
G.f.: (1-x)/((1-3*x)(1-5*x)).
E.g.f. 2*exp(5*x) - exp(3*x).
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MATHEMATICA
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CoefficientList[Series[(1 - x) / ((1 - 3 x) (1 - 5 x)), {x, 0, 40}], x] (* Vincenzo Librandi, Aug 09 2013 *)
LinearRecurrence[{8, -15}, {1, 7}, 30] (* Harvey P. Dale, Oct 14 2013 *)
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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