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 A127367 #9 Jul 13 2013 12:03:27 %S A127367 0,2,1,5,3,7,4,10,6,12,8,14,9,17,11,19,13,21,15,23,16,26,18,28,20,30, %T A127367 22,32,24,34,25,37,27,39,29,41,31,43,33,45,35,47,36,50,38,52,40,54,42, %U A127367 56,44,58,46,60,48,62,49,65,51,67,53,69,55,71,57,73,59,75,61,77,63,79,64 %N A127367 Inverse permutation to A127366. %C A127367 Let m be the largest number such that n >= m(m+1). If n is even, a(n) = n - m; otherwise a(n) = n + m + 1. %C A127367 a(A005408(n)) > 0; a(A005843(n)) <= 0. [_Reinhard Zumkeller_, Oct 12 2011] %H A127367 Reinhard Zumkeller, <a href="/A127367/b127367.txt">Table of n, a(n) for n = 0..10000</a> %H A127367 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A127367 (Haskell) %o A127367 a127367 n | even n = n - m + 1 %o A127367 | otherwise = n + m %o A127367 where m = length $ takeWhile (<= n) a002378_list %o A127367 -- _Reinhard Zumkeller_, Oct 12 2011 %Y A127367 Cf. A127366, A002378, A000194. %Y A127367 Cf. A002378 (oblong numbers). %K A127367 nonn %O A127367 0,2 %A A127367 _Franklin T. Adams-Watters_, Jan 11 2007