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 A076456 #22 Jul 05 2025 08:56:23
%S A076456 9,93,390,1110,2535,5019,8988,14940,23445,35145,50754,71058,96915,
%T A076456 129255,169080,217464,275553,344565,425790,520590,630399,756723,
%U A076456 901140,1065300,1250925,1459809,1693818,1954890,2245035,2566335,2920944,3311088,3739065,4207245
%N A076456 Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly three ways.
%D A076456 Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.
%H A076456 Vincenzo Librandi, <a href="/A076456/b076456.txt">Table of n, a(n) for n = 1..1000</a>
%H A076456 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A076456 a(n) = n*(n+1)*(6*n^2+4*n-1)/2.
%F A076456 G.f.: 3*x*(3+16*x+5*x^2)/(1-x)^5.
%p A076456 seq(1/2*n*(n+1)*(6*n^2+4*n-1),n=1..40);
%t A076456 CoefficientList[Series[3 (3 + 16 x + 5 x^2)/(1 - x)^5, {x, 0, 50}], x] (* _Vincenzo Librandi_, Dec 30 2013 *)
%o A076456 (Magma) [n*(n+1)*(6*n^2+4*n-1)/2: n in [1..50]]; // _Vincenzo Librandi_, Dec 30 2013
%Y A076456 Cf. A002417, A076454-A076459.
%K A076456 nonn,easy
%O A076456 1,1
%A A076456 _Floor van Lamoen_, Oct 13 2002