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 A277680 #7 May 03 2018 07:03:30
%S A277680 1,3,2,5,6,8,4,10,9,12,13,19,7,14,15,17,11,21,18,25,26,32,16,27,20,23,
%T A277680 24,34,33,40,28,30,22,36,35,38,41,51,31,42,43,49,39,53,50,61,62,72,29,
%U A277680 44,45,47,37,55,48,63,64,70,46,65,52,59,60,74,73,84,54
%N A277680 Inverse of the permutation A277679 of the natural numbers.
%C A277680 This is a permutation of the natural numbers, with inverse permutation A277679.
%H A277680 Clark Kimberling, <a href="/A277680/b277680.txt">Table of n, a(n) for n = 1..10000</a>
%H A277680 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%t A277680 x = Range[500];
%t A277680 NestWhile[# + 1 &, 1, (t = 1/2 # (1 + #);
%t A277680 x = Flatten[{Take[x, t],
%t A277680 Map[Reverse, Partition[Drop[x, t], # + 1]]}];
%t A277680 Length[x] > t) &]; x (* A277679 *)
%t A277680 Take[Ordering[#],Position[Differences[Sort[#]],Except[1]][[2]][[1]]]&[x] (* A277680 *) (* _Peter J. C. Moses_, Nov 13 2016 *)
%Y A277680 Cf. A000027, A277679, A007062, A057030.
%K A277680 nonn,look,easy
%O A277680 1,2
%A A277680 _Clark Kimberling_, Nov 14 2016