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 A224841 #13 Nov 11 2013 10:30:37
%S A224841 1,2,12,3,23,123,4,34,234,1234,5,45,345,2345,12345,6,56,456,3456,
%T A224841 23456,123456,7,67,567,4567,34567,234567,1234567,8,78,678,5678,45678,
%U A224841 345678,2345678,12345678,9,89,789,6789,56789,456789,3456789,23456789,123456789
%N A224841 Triangle T(n,k) read by rows: Substring of k digits of sequence A007376, ending at position n, 1 <= k <= n.
%C A224841 In contrast to sequence A162711, this sequence contains each substring without leading zero of A007376 at least once.
%H A224841 Reinhard Zumkeller, <a href="/A224841/b224841.txt">Rows n = 1..125 of table, flattened</a>
%o A224841 (PARI) for(i=1,9,for(j=1,i,for(k=i-j+1,i,print1(k));print1(",")))
%o A224841 (Haskell)
%o A224841 import Data.List (inits, tails)
%o A224841 a224841 n k = a224841_tabl !! (n-1) !! (k-1)
%o A224841 a224841_row n = a224841_tabl !! (n-1)
%o A224841 a224841_tabl = map
%o A224841 (reverse . map (read . concatMap show) . init . tails) $
%o A224841 tail $ inits a007376_list :: [[Integer]]
%o A224841 -- _Reinhard Zumkeller_, Nov 11 2013
%K A224841 nonn,easy,base,tabl
%O A224841 1,2
%A A224841 _M. F. Hasler_, Jul 22 2013