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A258129 Octagonal numbers (A000567) that are the sum of three consecutive octagonal numbers. 5
698901, 5102520783381, 37252493940331837461, 271973082264557457061125141, 1985621622943208359132836202790421, 14496630316026749501691464257547633057301, 105837027604506739193825102426073141683789429781, 772695182809023513889440668692977953487035688873891861 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
G.f.: -21*x*(x^2 -844482*x +33281)/((x-1)*(x^2 -7300802*x +1)).
EXAMPLE
698901 is in the sequence because Oct(483) = 698901 = 231296 + 232965 + 234640 = Oct(278) + Oct(279) + Oct(280).
MATHEMATICA
CoefficientList[Series[-21*x*(x^2 -844482*x +33281)/((x-1)*(x^2 -7300802*x +1)), {x, 0, 50}], x] (* G. C. Greubel, Oct 18 2017 *)
LinearRecurrence[{7300803, -7300803, 1}, {698901, 5102520783381, 37252493940331837461}, 20] (* Harvey P. Dale, Sep 16 2018 *)
PROG
(PARI) Vec(-21*x*(x^2 -844482*x +33281)/((x-1)*(x^2 -7300802*x +1)) + O('x^20))
CROSSREFS
Sequence in context: A205608 A205439 A027829 * A204496 A332850 A183835
KEYWORD
nonn,easy
AUTHOR
Colin Barker, May 21 2015
STATUS
approved

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Last modified July 22 14:07 EDT 2024. Contains 374499 sequences. (Running on oeis4.)