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A275060 Numbers n such that there exists x in N : (x+1)^3 - x^3 = 61*n^2. 2
1, 973, 947701, 923059801, 899059298473, 875682833652901, 852914180918627101, 830737536531909143473, 809137507667898587115601, 788099101730996691941451901, 767607715948483110052387035973, 747649127234720818194333031585801 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
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.
EXAMPLE
973 is in the sequence because 973^2 = 946729 = ((4387+1)^3-4387^3)/61.
MATHEMATICA
LinearRecurrence[{974, -1}, {1, 973}, 50] (* G. C. Greubel, Jul 15 2016 *)
PROG
(PARI) Vec(x*(1-x)/(1-974*x+x^2) + O(x^20))
CROSSREFS
Cf. A274972.
Sequence in context: A209045 A209017 A232409 * A251837 A251838 A251845
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jul 15 2016
STATUS
approved

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Last modified July 23 19:43 EDT 2024. Contains 374553 sequences. (Running on oeis4.)