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 A037839 #12 Jan 20 2018 12:24:01
%S A037839 0,0,0,0,0,0,1,0,1,2,3,4,5,2,1,0,1,2,3,4,3,2,1,0,1,2,3,4,3,2,1,0,1,2,
%T A037839 5,4,3,2,1,0,1,6,5,4,3,2,1,0,1,2,3,4,5,6,7,1,0,1,2,3,4,5,3,2,1,2,3,4,
%U A037839 5,5,4,3,2,3,4,5,7,6,5,4,3,4,5,9,8,7,6,5,4,5
%N A037839 a(n) = Sum{|d(i)-d(i-1)|: i=1,...,m}, where Sum{d(i)*7^i: i=0,1,...,m} is the base 7 representation of n.
%C A037839 This is the base-7 total variation sequence; see A297330. - _Clark Kimberling_, Jan 18 2017
%H A037839 Clark Kimberling, <a href="/A037839/b037839.txt">Table of n, a(n) for n = 1..10000</a>
%t A037839 b = 7; z = 120; t = Table[Total@Flatten@Map[Abs@Differences@# &, Partition[IntegerDigits[n, b], 2, 1]], {n, z}] (* cf. _Michael De Vlieger_, A037834 *)
%Y A037839 Cf. A297330.
%K A037839 nonn,base
%O A037839 1,10
%A A037839 _Clark Kimberling_
%E A037839 Updated by _Clark Kimberling_, Jan 20 2018