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 A259158 Positive triangular numbers (A000217) that are heptagonal numbers (A000566) divided by 2. 4

%I

%S 171,355817826,739874066553765,1538466018777014327028,

%T 3199027777735470191011289295,6651936797966044301302839516949686,

%U 13831784604089070782667939513452521937961,28761287297921206463992005998270360082445758120

%N Positive triangular numbers (A000217) that are heptagonal numbers (A000566) divided by 2.

%H Colin Barker, <a href="/A259158/b259158.txt">Table of n, a(n) for n = 1..158</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2079363,-2079363,1).

%F G.f.: -171*x*(1443*x+1) / ((x-1)*(x^2-2079362*x+1)).

%e 171 is in the sequence because 171 is the 18th triangular number, and 2*171 is the 12th heptagonal number.

%t LinearRecurrence[{2079363, -2079363, 1}, {171, 355817826, 739874066553765}, 20] (* _Vincenzo Librandi_, Jun 20 2015 *)

%o (PARI) Vec(-171*x*(1443*x+1) / ((x-1)*(x^2-2079362*x+1)) + O(x^20))

%Y Cf. A000217, A000566, A259156, A259157, A259159-A259167.

%K nonn,easy

%O 1,1

%A _Colin Barker_, Jun 19 2015

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Last modified August 8 09:40 EDT 2022. Contains 356009 sequences. (Running on oeis4.)