|
|
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
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|