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 A076455 #19 Jul 05 2025 08:55:29
%S A076455 5,57,246,710,1635,3255,5852,9756,15345,23045,33330,46722,63791,85155,
%T A076455 111480,143480,181917,227601,281390,344190,416955,500687,596436,
%U A076455 705300,828425,967005,1122282,1295546,1488135,1701435,1936880,2195952,2480181
%N A076455 Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly two ways.
%D A076455 Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.
%H A076455 Vincenzo Librandi, <a href="/A076455/b076455.txt">Table of n, a(n) for n = 1..1000</a>
%H A076455 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A076455 G.f.: x*(5 + 32*x + 11*x^2)/(1 - x)^5.
%F A076455 a(n) = n*(n + 1)*(4*n^2 + 2*n - 1)/2.
%p A076455 seq(1/2*n*(n+1)*(4*n^2+2*n-1),n=1..40);
%t A076455 CoefficientList[Series[(5 + 32 x + 11 x^2)/(1 - x)^5, {x, 0, 50}], x] (* _Vincenzo Librandi_, Dec 30 2013 *)
%o A076455 (Magma) [n*(n+1)*(4*n^2+2*n-1)/2: n in [1..50]]; // _Vincenzo Librandi_, Dec 30 2013
%Y A076455 Cf. A002417, A076454-A076459.
%K A076455 nonn,easy
%O A076455 1,1
%A A076455 _Floor van Lamoen_, Oct 13 2002