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


%S 280,373212840,497012764340408,661878856450449219400,

%T 881433339438556519000044120,1173817118196415977287174306335208,

%U 1563188689740940473437573487667885475320,2081720262768492984525248323578863263574296200

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

%C Intersection of A000567 and A033579 (even octagonal numbers divided by 2). - _Michel Marcus_, Jun 20 2015

%H Colin Barker, <a href="/A259079/b259079.txt">Table of n, a(n) for n = 1..163</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1331715,-1331715,1).

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

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

%t LinearRecurrence[{1331715,-1331715,1},{280,373212840,497012764340408},20] (* _Harvey P. Dale_, Dec 04 2015 *)

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

%Y Cf. A000567, A075528, A107736, A259078.

%K nonn,easy

%O 1,1

%A _Colin Barker_, Jun 18 2015

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Last modified January 27 04:57 EST 2020. Contains 331291 sequences. (Running on oeis4.)