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 A076457 #17 Jul 05 2025 08:57:24
%S A076457 13,129,534,1510,3435,6783,12124,20124,31545,47245,68178,95394,130039,
%T A076457 173355,226680,291448,369189,461529,570190,696990,843843,1012759,
%U A076457 1205844,1425300,1673425,1952613,2265354,2614234,3001935,3431235,3905008,4426224,4997949,5623345
%N A076457 Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly four ways.
%D A076457 Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.
%H A076457 Vincenzo Librandi, <a href="/A076457/b076457.txt">Table of n, a(n) for n = 1..1000</a>
%H A076457 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A076457 a(n) = n*(n+1)*(8*n^2+6*n-1)/2.
%F A076457 G.f.: x*(13+64*x+19*x^2)/(1-x)^5.
%p A076457 seq(1/2*n*(n+1)*(8*n^2+6*n-1),n=1..40);
%t A076457 CoefficientList[Series[(13 + 64 x + 19 x^2)/(1 - x)^5, {x, 0, 50}], x] (* _Vincenzo Librandi_, Dec 30 2013 *)
%o A076457 (Magma) [n*(n+1)*(8*n^2+6*n-1)/2: n in [1..50]]; // _Vincenzo Librandi_, Dec 30 2013
%Y A076457 Cf. A002417, A076454-A076459.
%K A076457 nonn,easy
%O A076457 1,1
%A A076457 _Floor van Lamoen_, Oct 13 2002