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 A284381 #19 Jun 25 2025 14:46:06
%S A284381 5,8,55,58,85,88,555,558,585,588,855,858,885,888,5555,5558,5585,5588,
%T A284381 5855,5858,5885,5888,8555,8558,8585,8588,8855,8858,8885,8888,55555,
%U A284381 55558,55585,55588,55855,55858,55885,55888,58555,58558,58585,58588,58855,58858
%N A284381 Numbers k with digits 5 and 8 only.
%C A284381 All terms except the first are composite.
%H A284381 Michael S. Branicky, <a href="/A284381/b284381.txt">Table of n, a(n) for n = 1..10000</a>
%F A284381 a(n) = (A284380(n)+A284382(n))/2. - _Robert Israel_, Mar 28 2017
%t A284381 Join @@ ((FromDigits /@ Tuples[{5, 8}, #]) & /@ Range@ 5) (* _Giovanni Resta_, Mar 28 2017 *)
%o A284381 (Magma) [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {5, 8}];
%o A284381 (Python)
%o A284381 def a(n): return int(bin(n+1)[3:].replace('0', '5').replace('1', '8'))
%o A284381 print([a(n) for n in range(1, 45)]) # _Michael S. Branicky_, May 08 2021
%Y A284381 Numbers n with digits 5 and k only for k = 0 - 4 and 6 - 9: A169964 (k = 0), A276037 (k = 1), A072961 (k = 2), A284379 (k = 3), A256290 (k = 4), A256291 (k = 6), A284380 (k = 7), this sequence (k = 8), A284382 (k = 9).
%K A284381 nonn,base
%O A284381 1,1
%A A284381 _Jaroslav Krizek_, Mar 28 2017