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 A033551 #12 Sep 08 2022 08:44:51 %S A033551 1,3,7,13,20,28,38,50,64,79,95,113,133,154,177,201,227,254,284,314, %T A033551 346,380,415,452,491,531,573,616,661,707,755,804,855,908,962,1018, %U A033551 1075,1134,1195,1257,1320,1385,1452,1521 %N A033551 Closest integer to (Pi/4)*n^2. %H A033551 Harvey P. Dale, <a href="/A033551/b033551.txt">Table of n, a(n) for n = 1..1000</a> %F A033551 a(n) = round( (Pi/4) * n^2 ). %e A033551 a(3)=7, since 3^2*Pi/4 = 7.06858347. %p A033551 seq(round((1/4)*Pi*n^2), n = 1..50); # _G. C. Greubel_, Oct 12 2019 %t A033551 Round[Pi/4 Range[50]^2] (* _Harvey P. Dale_, May 11 2016 *) %o A033551 (PARI) a(n) = round((Pi/4) * n^2); \\ _Michel Marcus_, Sep 02 2013 %o A033551 (Magma) R:= RealField(20); [Round(Pi(R)*n^2/4): n in [1..50]]; // _G. C. Greubel_, Oct 12 2019 %o A033551 (Sage) [round(pi*n^2/4) for n in (1..50)] # _G. C. Greubel_, Oct 12 2019 %o A033551 (GAP) List([1..50], n-> Int(Round(Atan(1.0)*n^2)) ); # _G. C. Greubel_, Oct 12 2019 %Y A033551 Approximation for A051233. %K A033551 easy,nonn %O A033551 1,2 %A A033551 Joe K. Crump (joecr(AT)carolina.rr.com)