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A016782
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a(n) = (3*n+1)^6.
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8
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1, 4096, 117649, 1000000, 4826809, 16777216, 47045881, 113379904, 244140625, 481890304, 887503681, 1544804416, 2565726409, 4096000000, 6321363049, 9474296896, 13841287201, 19770609664, 27680640625, 38068692544, 51520374361, 68719476736, 90458382169, 117649000000
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (1 + 4089*x + 88998*x^2 + 262438*x^3 + 154113*x^4 + 15177*x^5 + 64*x^6)/(1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7). (End)
Sum_{n>=0} 1/a(n) = PolyGamma(5, 1/3)/87480. - Amiram Eldar, Mar 29 2022
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MATHEMATICA
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LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {1, 4096, 117649, 1000000, 4826809, 16777216, 47045881}, 20] (* Harvey P. Dale, Sep 30 2016 *)
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PROG
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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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