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 A211784 #21 Nov 23 2023 15:59:32
%S A211784 1,7,16,29,45,66,89,117,148,183,221,264,309,359,412,469,529,594,661,
%T A211784 733,808,887,969,1056,1145,1239,1336,1437,1541,1650,1761,1877,1996,
%U A211784 2119,2245,2376,2509,2647,2788,2933,3081,3234,3389,3549,3712,3879
%N A211784 a(n) = n^2 + floor(n^2/2) + floor(n^2/3).
%C A211784 Row 3 of the array A211783.
%H A211784 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,0,-1,-1,1).
%F A211784 a(n) = a(n-1)+a(n-2)-a(n-4)-a(n-5)+a(n-6) for n>=7.
%F A211784 G.f.: x*(1+6*x+8*x^2+6*x^3+x^4)/((1-x)^3*(1+2*x+2*x^2+x^3)). - _Bruno Berselli_, May 06 2012
%F A211784 a(n) = (66*n^2 + 9*(-1)^n - 17 - 4*A061347(n))/36. - _Stefano Spezia_, Nov 23 2023
%t A211784 f[n_, m_] := Sum[Floor[n^2/k], {k, 1, m}]
%t A211784 t = Table[f[n, 3], {n, 1, 90}]
%t A211784 FindLinearRecurrence[t]
%t A211784 LinearRecurrence[{1, 1, 0, -1, -1, 1},{1, 7, 16, 29, 45, 66},46] (* _Ray Chandler_, Aug 02 2015 *)
%o A211784 (Magma) [&+[Floor(n^2/k): k in [1..3]]: n in [1..46]]; // _Bruno Berselli_, May 06 2012
%Y A211784 Cf. A061347, A211701.
%K A211784 nonn,easy
%O A211784 1,2
%A A211784 _Clark Kimberling_, Apr 20 2012