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 A209387 #12 Jan 04 2018 01:34:12
%S A209387 1,3,7,13,5,15,27,41,25,43,23,45,21,47,19,49,17,51,87,125,85,127,83,
%T A209387 37,85,35,87,33,89,31,91,29,93,159,227,157,229,155,79,157,77,159,75,
%U A209387 161,73,163,71,165,69,167,67,169,65,171,63,173,61,175,59,177,57,179,55,181,53,183,315,449,313,451,311
%N A209387 a(n) = 2*A005132(n) + 1.
%C A209387 This is the odd-numbers version of Recamán's sequence A005132: a(0)=1; for n>0, a(n) = a(n-1)-(2n+1) if that number is >= 0 and not already in the sequence, otherwise a(n) = a(n-1)+(2n+1).
%H A209387 G. C. Greubel, <a href="/A209387/b209387.txt">Table of n, a(n) for n = 0..1000</a>
%t A209387 f[s_List]:= Block[{a = s[[-1]], len = Length@s}, Append[s, If[a > len && ! MemberQ[s, a - len], a - len, a + len]]]; A005132:= Nest[f, {0}, 130]; Table[2*A005132[[n]] + 1, {n, 1, 50}] (* _G. C. Greubel_, Jan 03 2018 *)
%Y A209387 Cf. A005132, A209386.
%K A209387 nonn
%O A209387 0,2
%A A209387 _N. J. A. Sloane_, Mar 07 2012