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 A187840 #13 Feb 12 2018 11:29:07
%S A187840 2,5,6,10,11,13,16,18,20,23,25,27,29,32,34,36,39,40,43,45,48,49,53,54,
%T A187840 57,59,61,64,66,67,70,72,75,77,79,81,84,87,88,91,93,95,97,100,102,105,
%U A187840 106,109,110,113,115,118,120,122,125,127,129,131,133,136,138,141,143,145,148,149,152,154,157,158,161,163,165,168,170
%N A187840 Complement of A187839.
%C A187840 See A187224.
%H A187840 G. C. Greubel, <a href="/A187840/b187840.txt">Table of n, a(n) for n = 1..10000</a>
%t A187840 r=2^(1/2);
%t A187840 seqA = Table[Floor[r*n-1/2], {n, 1, 220}]
%t A187840 seqB = Table[n, {n, 1, 220}]; (* A000027 *)
%t A187840 jointRank[{seqA_,
%t A187840 seqB_}] := {Flatten@Position[#1, {_, 1}],
%t A187840 Flatten@Position[#1, {_, 2}]} &[
%t A187840 Sort@Flatten[{{#1, 1} & /@ seqA, {#1, 2} & /@ seqB}, 1]];
%t A187840 limseqU =
%t A187840 FixedPoint[jointRank[{seqA, #1[[1]]}] &,
%t A187840 jointRank[{seqA, seqB}]][[1]] (* A187839 *)
%t A187840 Complement[Range[Length[seqA]], limseqU] (* A187840 *)
%t A187840 (* _Peter J. C. Moses_, Mar 13 2011 *)
%Y A187840 Cf. A187224, A187839.
%K A187840 nonn
%O A187840 1,1
%A A187840 _Clark Kimberling_, Mar 13 2011