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