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 A061875 #11 Jun 18 2021 02:49:00
%S A061875 6,17,28,39,60,71,82,93,105,116,127,138,149,170,181,192,204,215,226,
%T A061875 237,248,259,280,291,303,314,325,336,347,358,369,390,402,413,424,435,
%U A061875 446,457,468,479,501,512,523,534,545,556,567,578,589,600,611,622,633,644
%N A061875 |First digit - second digit + third digit - fourth digit ...| = 6.
%H A061875 Harvey P. Dale, <a href="/A061875/b061875.txt">Table of n, a(n) for n = 1..1000</a>
%t A061875 Do[ a = IntegerDigits[ n ]; l = Length[ a ]; e = o = {}; Do[ o = Append[ o, a[[ 2k - 1 ] ] ], {k, 1, l/2 + .5} ]; Do[ e = Append[ e, a[[ 2k ] ] ], {k, 1, l/2} ]; If[ Abs[ Apply[ Plus, o ] - Apply[ Plus, e ] ] == 6, Print[ n ] ], {n, 1, 1000} ]
%t A061875 Select[Range[700],Abs[Total[Times@@@Partition[Riffle[IntegerDigits[#],{1,-1},{2,-1,2}],2]]]==6&] (* _Harvey P. Dale_, May 21 2020 *)
%o A061875 (Python)
%o A061875 def ok(n): return abs(sum(int(d)*(-1)**i for i, d in enumerate(str(n))))==6
%o A061875 print(list(filter(ok, range(645)))) # _Michael S. Branicky_, Jun 17 2021
%Y A061875 Cf. A008593, A060978-A060980, A060982, A061470-A061479, A061870-A061882.
%K A061875 nonn,base,easy
%O A061875 1,1
%A A061875 _Robert G. Wilson v_, May 10 2001