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 A284633 #15 Sep 08 2022 08:46:19
%S A284633 3,6,33,36,63,66,333,336,363,366,633,636,663,666,3333,3336,3363,3366,
%T A284633 3633,3636,3663,3666,6333,6336,6363,6366,6633,6636,6663,6666,33333,
%U A284633 33336,33363,33366,33633,33636,33663,33666,36333,36336,36363,36366,36633,36636
%N A284633 Numbers n with digits 3 and 6 only.
%C A284633 All terms after 3 are composite.
%F A284633 a(n) = 3*A007931(n). - _Michel Marcus_, Mar 30 2017
%t A284633 Table[Map[FromDigits, Tuples[{3, 6}, {k}]], {k, 5}] // Flatten (* _Michael De Vlieger_, Mar 30 2017 *)
%o A284633 (Magma) [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {3, 6}]
%Y A284633 Cf. A007931.
%Y A284633 Numbers n with digits 6 and k only for k = 0..5 and 7..9: A204093 (k = 0), A284293 (k = 1), A284632 (k = 2), this sequence (k = 3), A284634 (k = 4), A256291 (k = 5), A256292 (k = 7), A284635 (k = 8), A284636 (k = 9).
%K A284633 nonn,base
%O A284633 1,1
%A A284633 _Jaroslav Krizek_, Mar 30 2017