A259079 Octagonal numbers (A000567) that are other octagonal numbers divided by 2.

280, 373212840, 497012764340408, 661878856450449219400, 881433339438556519000044120, 1173817118196415977287174306335208, 1563188689740940473437573487667885475320, 2081720262768492984525248323578863263574296200

Offset

1,1

Comments

Intersection of A000567 and A033579 (even octagonal 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