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 A275649 #22 Dec 25 2016 12:08:53
%S A275649 2,14,112,997,8982,82305,764092,7159654,67581778,641696858,6122456540,
%T A275649 58649349611,563729377405,5434188304040,52515178669973,508607849995010
%N A275649 Number of squarefree odd numbers k > 1 less than 10^n such that k is a sum of two squares.
%C A275649 This sequence gives the values of the counting function U(x), whose values are given in table 2 on page 359 of Shiu, 1986.
%H A275649 P. Shiu, <a href="http://dx.doi.org/10.1090/S0025-5718-1986-0842141-1">Counting sums of two squares: the Meissel-Lehmer method</a>, Mathematics of Computation, 47 (1986), 351-360.
%t A275649 Table[Count[Range[1, 10^n, 2], k_ /; SquareFreeQ@ k && SquaresR[2, k] > 0], {n, 6}] (* _Michael De Vlieger_, Aug 04 2016 *)
%Y A275649 Cf. A164775: W(x), A275650: V(x).
%K A275649 nonn,more
%O A275649 1,1
%A A275649 _Felix Fröhlich_, Aug 04 2016
%E A275649 a(7), a(11) and a(12) corrected and a(13)-a(16) added by _Hiroaki Yamanouchi_, Dec 25 2016