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 A051233 #25 Sep 06 2021 13:30:44 %S A051233 1,4,9,12,21,32,37,52,69,80,97,112,137,156,177,208,225,256,293,316, %T A051233 349,384,421,448,489,540,577,616,665,716,749,812,861,912,973,1020, %U A051233 1085,1124,1201,1264,1313,1396,1457,1528,1597,1664,1741,1804,1885,1976,2053 %N A051233 Number of unit squares at least 50% covered by a circle inscribed in an integer square of size n X n. %C A051233 From _Robert G. Wilson v_, Mar 20 2017: (Start) %C A051233 For n odd, the center of the circle is in the middle of the center square and thus a(2n-1) == 1 (mod 4). %C A051233 For n even, the center of the circle is at the four corners of the center 4 squares and thus a(2n) == 0 (mod 4). (End) %H A051233 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a051/A051233.java">Java program</a> (github) %F A051233 Conjecture: a(n) <= A124623(n) with equality in most cases. - _Sean A. Irvine_, Sep 03 2021 %e A051233 a(2)=4 because an inscribed circle in a 2 X 2 grid covers at least 50% of each of the unit squares within it. %Y A051233 Cf. A124623, A120883, A036704. %K A051233 nonn,more %O A051233 1,2 %A A051233 Joe K. Crump (joecr(AT)carolina.rr.com) %E A051233 Data corrected by _Sean A. Irvine_, Sep 02 2021