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 A262491 #8 May 17 2020 11:16:47
%S A262491 43,120,549,3783,17214,47629,216688,1490884,6782665,18766098,85374915,
%T A262491 587404905,2672353188,7393795375,33637500214,231436042078,
%U A262491 1052900373799,2913136612044,13253089709793,91185213174219,414840074924010,1147768431350353,5221683708158620
%N A262491 The index of the first of two consecutive positive triangular numbers (A000217) the sum of which is equal to the sum of eleven consecutive positive triangular numbers.
%C A262491 For the index of the first of the corresponding eleven consecutive triangular numbers, see A116476.
%H A262491 Colin Barker, <a href="/A262491/b262491.txt">Table of n, a(n) for n = 1..1000</a>
%H A262491 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,394,-394,0,0,-1,1).
%F A262491 G.f.: -x*(10*x^8+33*x^6+77*x^5-3511*x^4+3234*x^3+429*x^2+77*x+43) / ((x-1)*(x^8-394*x^4+1)).
%e A262491 43 is in the sequence because T(43)+T(44) = 946+990 = 1936 = 91+...+276 = T(13)+...+T(23), where T(k) is the k-th triangular number.
%t A262491 LinearRecurrence[{1,0,0,394,-394,0,0,-1,1},{43,120,549,3783,17214,47629,216688,1490884,6782665},30] (* _Harvey P. Dale_, May 17 2020 *)
%o A262491 (PARI) Vec(-x*(10*x^8+33*x^6+77*x^5-3511*x^4+3234*x^3+429*x^2+77*x+43)/((x-1)*(x^8-394*x^4+1)) + O(x^30))
%Y A262491 Cf. A000217, A116476, A262489, A262490, A262492.
%K A262491 nonn,easy
%O A262491 1,1
%A A262491 _Colin Barker_, Sep 24 2015