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A030240
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Scaled Chebyshev U-polynomials evaluated at sqrt(7)/2.
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13
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1, 7, 42, 245, 1421, 8232, 47677, 276115, 1599066, 9260657, 53631137, 310593360, 1798735561, 10416995407, 60327818922, 349375764605, 2023335619781, 11717718986232, 67860683565157, 393000752052475, 2275980479411226, 13180858091511257, 76334143284700217
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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) = 7*a(n-1)-7*a(n-2), a(-1)=0, a(0)=1; a(n)=sqrt(7)^n*U(n, sqrt(7)/2); G.f.: 1/(1-7*x+7*x^2); a(2*k)=7^k*A030221(k); a(2*k-1)=7^k*A004254(k)
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MATHEMATICA
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PROG
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(Sage) [lucas_number1(n, 7, 7) for n in range(1, 21)] # Zerinvary Lajos, Apr 23 2009
(PARI) Vec(1/(1-7*x+7*x^2) + O(x^30)) \\ Colin Barker, Jun 14 2015
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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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