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 A169964 #27 Oct 30 2023 11:35:31
%S A169964 0,5,50,55,500,505,550,555,5000,5005,5050,5055,5500,5505,5550,5555,
%T A169964 50000,50005,50050,50055,50500,50505,50550,50555,55000,55005,55050,
%U A169964 55055,55500,55505,55550,55555,500000,500005,500050,500055,500500,500505,500550,500555
%N A169964 Numbers whose decimal expansion contains only 0's and 5's.
%H A169964 Reinhard Zumkeller, <a href="/A169964/b169964.txt">Table of n, a(n) for n = 1..10000</a>
%H A169964 <a href="/index/Ca#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>
%F A169964 a(n+1) = Sum_{k>=0} A030308(n,k)*A093143(k+1). - _Philippe Deléham_, Oct 16 2011
%F A169964 a(n) = 5 * A007088(n-1).
%t A169964 Map[FromDigits,Tuples[{0,5},6]] (* _Paolo Xausa_, Oct 30 2023 *)
%o A169964 (PARI) print1(0);for(d=1,5,for(n=2^(d-1),2^d-1,print1(", ");forstep(i=d-1,0,-1,print1((n>>i)%2*5)))) \\ _Charles R Greathouse IV_, Nov 16 2011
%o A169964 (Haskell)
%o A169964 a169964 n = a169964_list !! (n-1)
%o A169964 a169964_list = map (* 5) a007088_list
%o A169964 -- _Reinhard Zumkeller_, Jan 10 2012
%Y A169964 Cf. A007088, A014263, A169965, A169966, A169967.
%Y A169964 Cf. A078244, A204093, A204094, A204095, A097256.
%K A169964 nonn,base,easy
%O A169964 1,2
%A A169964 _N. J. A. Sloane_, Aug 07 2010