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 A183139 #10 Sep 08 2022 08:45:55 %S A183139 0,1,3,5,8,12,16,21,27,34,41,49,58,67,77,88,100,112,125,139,153,168, %T A183139 184,200,217,235,254,273,293,314,335,357,380,404,428,453,479,505,532, %U A183139 560,588,617,647,678,709,741,774,807,841,876 %N A183139 a(n) = [1/r]+[2/r]+...+[n/r], where r=sqrt(2) and []=floor. %C A183139 A183139 + A183140 = A000217 (the triangular numbers). %H A183139 G. C. Greubel, <a href="/A183139/b183139.txt">Table of n, a(n) for n = 1..10000</a> %F A183139 a(n) = [1/r]+[2/r]+...+[n/r], where r=sqrt(2) and []=floor. %t A183139 Accumulate[Floor[Range[100]/(Sqrt[2])]] (* _G. C. Greubel_, Apr 10 2018 *) %o A183139 (PARI) for(n=1, 100, print1(sum(k=1,n, floor(k/sqrt(2))), ", ")) \\ _G. C. Greubel_, Apr 10 2018 %o A183139 (Magma) [(&+[Floor(k/Sqrt(2)):k in [1..n]]): n in [1..100]]; // _G. C. Greubel_, Apr 10 2018 %Y A183139 Cf. A183139, A183140, A000217. %K A183139 nonn %O A183139 1,3 %A A183139 _Clark Kimberling_, Dec 26 2010