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A259079 Octagonal numbers (A000567) that are other octagonal numbers divided by 2. 2
280, 373212840, 497012764340408, 661878856450449219400, 881433339438556519000044120, 1173817118196415977287174306335208, 1563188689740940473437573487667885475320, 2081720262768492984525248323578863263574296200 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Intersection of A000567 and A033579 (even octogonal numbers divided by 2). - Michel Marcus, Jun 20 2015

LINKS

Colin Barker, Table of n, a(n) for n = 1..163

Index entries for linear recurrences with constant coefficients, signature (1331715,-1331715,1).

FORMULA

G.f.: -8*x*(x^2+41580*x+35) / ((x-1)*(x^2-1331714*x+1)).

EXAMPLE

280 is in the sequence because 280 is the 10th octagonal number, and 2*280 is the 14th octagonal number.

MATHEMATICA

LinearRecurrence[{1331715, -1331715, 1}, {280, 373212840, 497012764340408}, 20] (* Harvey P. Dale, Dec 04 2015 *)

PROG

(PARI) Vec(-8*x*(x^2+41580*x+35)/((x-1)*(x^2-1331714*x+1)) + O(x^20))

CROSSREFS

Cf. A000567, A075528, A107736, A259078.

Sequence in context: A255498 A091034 A294165 * A296506 A308456 A175145

Adjacent sequences:  A259076 A259077 A259078 * A259080 A259081 A259082

KEYWORD

nonn,easy

AUTHOR

Colin Barker, Jun 18 2015

STATUS

approved

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Last modified December 14 22:42 EST 2019. Contains 329987 sequences. (Running on oeis4.)