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 A212439 #19 Apr 08 2025 08:44:55
%S A212439 1,3,5,6,8,11,13,15,17,19,20,22,24,27,29,30,32,35,37,38,40,42,45,47,
%T A212439 49,51,52,54,56,59,61,63,65,67,69,70,72,74,77,79,81,83,85,86,88,90,93,
%U A212439 94,96,99,101,102,104,106,108,111,113,115,116,118,120,123,125
%N A212439 a(n) = 2*n + A181935(n) mod 2.
%C A212439 A212444 gives iterations starting from 0.
%H A212439 Reinhard Zumkeller, <a href="/A212439/b212439.txt">Table of n, a(n) for n = 0..8191</a>
%H A212439 Benjamin Chaffin, John P. Linderman, N. J. A. Sloane, and Allan R. Wilks, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL16/Sloane/sloane3.html">On Curling Numbers of Integer Sequences</a>, Journal of Integer Sequences, Vol. 16 (2013), Article 13.4.3.
%H A212439 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.
%F A212439 a(n) = 2*n + A212412(n): concatenation of binary representation of n and the parity of its curling number.
%t A212439 f[n_, e_] := Module[{d = IntegerDigits[n, 2^e]}, Length[Split[d][[-1]]] - If[SameQ @@ d && Mod[n, 2^e] < 2^(e - 1), 1, 0]]; a[n_] := 2*n + Mod[Max[Table[f[n, e], {e, Range[Max[1, Floor[Log2[n]]]]}]], 2]; a[0] = 1; Array[a, 100, 0] (* _Amiram Eldar_, Apr 08 2025 *)
%o A212439 (Haskell)
%o A212439 a212439 n = 2 * n + a212412 n
%Y A212439 Cf. A014601, A007088, A181935, A212412, A212444.
%K A212439 nonn,base
%O A212439 0,2
%A A212439 _Reinhard Zumkeller_, May 17 2012