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 A064426 #14 Sep 10 2018 10:12:26
%S A064426 1,2,2,-3,6,3,-4,2,-5,10,3,-4,-7,14,3,-8,4,2,-11,22,-6,3,-5,10,-7,-2,
%T A064426 -13,26,-3,-4,2,-17,34,-9,-4,-19,38,-12,-5,4,2,-23,46,-21,2,2,2,2,-7,
%U A064426 14,-3,-5,10,5,-12,-29,58,-21,-4,-31,62,-21,-8,4,6,-37,74,-36,3,-2,4,2,-41,82,-42,3,-7,11,-2,-43
%N A064426 First differences of A064413.
%H A064426 Reinhard Zumkeller, <a href="/A064426/b064426.txt">Table of n, a(n) for n = 1..10000</a>
%H A064426 J. C. Lagarias, E. M. Rains and N. J. A. Sloane, <a href="http://arXiv.org/abs/math.NT/0204011">The EKG sequence</a>, Exper. Math. 11 (2002), 437-446.
%H A064426 <a href="/index/Ed#EKG">Index entries for sequences related to EKG sequence</a>
%t A064426 ekg[s_] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]]; Nest[ekg, {1, 2}, 100] // Differences (* _Jean-François Alcover_, Sep 10 2018, after _Robert G. Wilson v_ *)
%o A064426 (Haskell)
%o A064426 a064426 n = a064426_list !! (n-1)
%o A064426 a064426_list = zipWith (-) (tail a064413_list) a064413_list
%o A064426 -- _Reinhard Zumkeller_, Sep 17 2001
%K A064426 sign
%O A064426 1,2
%A A064426 _N. J. A. Sloane_, Oct 02 2001