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 A251927 #8 Dec 08 2016 09:51:53
%S A251927 0,8,76,1518,12986,111034,2190396,18727244,160112392,3158550954,
%T A251927 27004674302,230881959670,4554628286712,38940721617680,
%U A251927 332931625733188,6567770830889190,56152493568021698,480087173425298866,9470720983513926708,80971856784365672276
%N A251927 Numbers n such that the sum of the triangular numbers T(n) and T(n+1) is equal to a heptagonal number H(m) for some m.
%C A251927 Also nonnegative integers x in the solutions to 2*x^2-5*y^2+4*x+3*y+2+2 = 0, the corresponding values of y being A046195.
%H A251927 Colin Barker, <a href="/A251927/b251927.txt">Table of n, a(n) for n = 1..950</a>
%H A251927 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,1442,-1442,0,-1,1).
%F A251927 G.f.: 2*x^2*(x^5+4*x^4+34*x^3-721*x^2-34*x-4) / ((x-1)*(x^6-1442*x^3+1)).
%e A251927 8 is in the sequence because T(8)+T(9) = 36+45 = 81 = H(6).
%t A251927 LinearRecurrence[{1,0,1442,-1442,0,-1,1},{0,8,76,1518,12986,111034,2190396},20] (* _Harvey P. Dale_, Dec 08 2016 *)
%o A251927 (PARI) concat(0, Vec(2*x^2*(x^5+4*x^4+34*x^3-721*x^2-34*x-4)/((x-1)*(x^6-1442*x^3+1)) + O(x^100)))
%Y A251927 Cf. A000217, A000566, A046195.
%K A251927 nonn,easy
%O A251927 1,2
%A A251927 _Colin Barker_, Dec 11 2014