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 A180426 #21 Feb 16 2025 08:33:13 %S A180426 3,30,265,2351,21062,191630,1766955,16465551,154749588,1464326721, %T A180426 13932672360,133165432342,1277568139729,12295904124627, %U A180426 118665023703067,1147922359531155 %N A180426 The number of n-digit numbers requiring 2 nonzero squares in their representation as sum of squares. %C A180426 A049415(n) + a(n) + A180429(n) + A180347(n) = A052268(n) %H A180426 Eric W. Weisstein: <a href="https://mathworld.wolfram.com/LagrangesFour-SquareTheorem.html">MathWorld -- Lagrange's Four-Square Theorem.</a> %H A180426 Eric W. Weisstein: <a href="https://mathworld.wolfram.com/SumofSquaresFunction.html">MathWorld -- Sum of Squares Function.</a> %F A180426 a(n) = A180416(n)-A180416(n-1) for n>1. %Y A180426 Cf. A000404, A180416. %K A180426 nonn,more,base %O A180426 1,1 %A A180426 _Martin Renner_, Jan 19 2011 %E A180426 a(5)-a(8) from _Alois P. Heinz_, Jan 20 2011 %E A180426 a(9)-a(10) from _Donovan Johnson_, Jul 01 2011 %E A180426 a(10) corrected and a(11)-a(16) added by _Hiroaki Yamanouchi_, Aug 30 2014