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 A061871 #2 Mar 30 2012 17:30:32
%S A061871 2,13,20,24,31,35,42,46,53,57,64,68,75,79,86,97,101,112,123,130,134,
%T A061871 141,145,152,156,163,167,174,178,185,189,196,200,211,222,233,240,244,
%U A061871 251,255,262,266,273,277,284,288,295,299,310,321,332,343,350,354,361
%N A061871 |First digit - second digit + third digit - fourth digit ...| = 2.
%t A061871 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 ] ] == 2, Print[ n ] ], {n, 1, 1000} ]
%Y A061871 Cf. A008593, A060978-A060980, A060982, A061470-A061479, A061870-A061882.
%K A061871 nonn,base,easy
%O A061871 1,1
%A A061871 _Robert G. Wilson v_, May 10 2001