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A275060
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Numbers n such that there exists x in N : (x+1)^3 - x^3 = 61*n^2.
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2
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1, 973, 947701, 923059801, 899059298473, 875682833652901, 852914180918627101, 830737536531909143473, 809137507667898587115601, 788099101730996691941451901, 767607715948483110052387035973, 747649127234720818194333031585801
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OFFSET
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1,2
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LINKS
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Colin Barker, Table of n, a(n) for n = 1..300
Index entries for linear recurrences with constant coefficients, signature (974,-1).
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FORMULA
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G.f.: x*(1-x) / (1-974*x+x^2).
a(n) = 974*a(n-1) - a(n-2) for n>2.
a(n) = ((487 + 36*sqrt(183))^(-n)*(2 - 9*sqrt(3/61) + (2+9*sqrt(3/61))* (487 + 36*sqrt(183))^(2*n)))/4.
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EXAMPLE
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973 is in the sequence because 973^2 = 946729 = ((4387+1)^3-4387^3)/61.
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MATHEMATICA
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LinearRecurrence[{974, -1}, {1, 973}, 50] (* G. C. Greubel, Jul 15 2016 *)
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PROG
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(PARI) Vec(x*(1-x)/(1-974*x+x^2) + O(x^20))
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CROSSREFS
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Cf. A274972.
Sequence in context: A209045 A209017 A232409 * A251837 A251838 A251845
Adjacent sequences: A275057 A275058 A275059 * A275061 A275062 A275063
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KEYWORD
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nonn,easy
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AUTHOR
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Colin Barker, Jul 15 2016
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STATUS
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approved
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