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 A154513 #8 Mar 05 2019 00:07:00
%S A154513 6,8,1,1,1,1,2,2,2,2,2,3,3,3,3,4,4,4,5,5,5,6,6,6,7,7,7,7,8,8,9,9,9,9,
%T A154513 1,4,6,0,1,1,1,7,1,1,1,3,8,3,1,5,1,1,1,1,1,1,1,3,5,1,8,1,8,1,0,1,7,0,
%U A154513 1,5,1,1,2,5,8,2,2,5,2,9,2,4,2,8,0,2,2,8,2,1,2,2,2,2,6,2,2,2,5,2,5,2,2,2,5
%N A154513 The prime(n)-th digit of the concatenated composites.
%C A154513 The concatenated composites are A129808, the initial 1 removed.
%F A154513 a(n) = A129808(prime(n)+1).
%p A154513 a129808 := [1 ] : for n from 4 to 400 do if not isprime(n) then a129808 := [op(a129808), op(ListTools[Reverse](convert(n,base,10))) ] ; fi; od:
%p A154513 for n from 1 do p := ithprime(n) ; printf("%d,", op(p+1,a129808) ) ; od: # _R. J. Mathar_, Aug 03 2009
%t A154513 nn=700;With[{c=Flatten[IntegerDigits/@Complement[Range[4,nn],Prime[Range[ PrimePi[nn]]]]]}, Flatten[Table[Take[c,{n,n}],{n,Prime[Range[ PrimePi[ nn]]]}]]] (* _Harvey P. Dale_, Nov 22 2013 *)
%Y A154513 Cf. A000040, A002808, A154513, A154520.
%K A154513 nonn,base
%O A154513 1,1
%A A154513 _Juri-Stepan Gerasimov_, Jan 11 2009
%E A154513 Edited and corrected by _R. J. Mathar_, Aug 03 2009