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 A048376 #13 Jun 25 2016 05:51:05
%S A048376 1,22,333,4444,55555,666666,7777777,88888888,999999999,1,11,122,1333,
%T A048376 14444,155555,1666666,17777777,188888888,1999999999,22,221,2222,22333,
%U A048376 224444,2255555,22666666,227777777,2288888888,22999999999,333,3331
%N A048376 Replace each 1 in decimal expansion of n with 1 1's, each 2 with 2 2's, etc. (0 vanishes).
%H A048376 Harvey P. Dale, <a href="/A048376/b048376.txt">Table of n, a(n) for n = 1..1000</a>
%e A048376 12 -> 122, 123->122333.
%t A048376 With[{rules=Table[n->Table[n,{n}],{n,0,9}]},Table[FromDigits[ Flatten[ IntegerDigits[x]/.rules]],{x,40}]] (* _Harvey P. Dale_, Oct 09 2011 *)
%o A048376 (PARI) A048376(n)={sum(i=1,#n=concat( apply( t->vector(t,i,t),digits(n) )),n[i]*10^(#n-i))} \\ _M. F. Hasler_, Jan 23 2013
%Y A048376 Cf. A048377, A057628, A057630.
%K A048376 nonn,easy,base,nice
%O A048376 1,2
%A A048376 _Patrick De Geest_, Mar 15 1999