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 A248365 #13 Nov 07 2014 00:27:02
%S A248365 44,88,1212,1616,2020,2424,2828,3232,3636,4040,4444,4848,5252,5656,
%T A248365 6060,6464,6868,7272,7676,8080,8484,8888,9292,9696,100100,104104,
%U A248365 108108,112112,116116,120120,124124,128128,132132,136136,140140,144144,148148,152152,156156
%N A248365 4n concatenated with itself.
%H A248365 Michael De Vlieger, <a href="/A248365/b248365.txt">Table of n, a(n) for n = 1..10000</a>
%t A248365 a248038[n_Integer] := Module[{m, t}, m := ToString[4 n ]; ToExpression[m <> m]]; a248038 /@ Range[50]; (* _Michael De Vlieger_, Nov 06 2014 *)
%o A248365 (Python) {print(str(4*n)*2,end=', ') for n in range(1,50)} # _Derek Orr_, Oct 05 2014
%Y A248365 Cf. A020338 (n), A248038 (3n), A248422 (2n).
%K A248365 nonn,base,easy
%O A248365 1,1
%A A248365 _Jacy Fang_, Oct 05 2014