This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A097579 #18 Aug 03 2025 18:55:18
%S A097579 1,28,946,32131,1091503,37078966,1259593336,42789094453,1453569618061,
%T A097579 49378577919616,1677418079648878,56982836130142231,
%U A097579 1935739010345186971,65758143515606214778,2233841140520266115476,75884840634173441711401
%N A097579 Triangular numbers k such that 2*k-1 is also a triangular number.
%H A097579 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (35, -35, 1).
%F A097579 G.f.: x*(1-7*x+x^2)/((1-x)*(1-34*x+x^2)).
%t A097579 CoefficientList[ Series[x*(1 - 7*x + x^2)/((1 - x)*(1 - 34*x + x^2)), {x, 0, 16}], x] (* _Robert G. Wilson v_, Sep 01 2004 *)
%t A097579 LinearRecurrence[{35,-35,1},{1,28,946},20] (* _Harvey P. Dale_, Aug 03 2025 *)
%Y A097579 Cf. A075528, A124174.
%K A097579 easy,nonn
%O A097579 1,2
%A A097579 _Vladeta Jovovic_, Aug 29 2004
%E A097579 More terms from _Robert G. Wilson v_, Sep 01 2004