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 A037383 #22 May 09 2024 14:23:34
%S A037383 1,2,13,51,63,67,68,79,84,91,99,105,134,205,211,246,252,345,351,352,
%T A037383 354,355,357,358,359,360,361,362,363,364,366,373,380,387,394,401,406,
%U A037383 441,442,443,444,445,446,447,448,449,454,455,457
%N A037383 Numbers k such that every base-3 digit of k is a base-7 digit of k.
%H A037383 Reinhard Zumkeller, <a href="/A037383/b037383.txt">Table of n, a(n) for n = 1..10000</a>
%t A037383 Select[Range[500],Complement[Union[IntegerDigits[#,3]],Union[IntegerDigits[#,7]]]=={}&] (* _Harvey P. Dale_, Jan 28 2024 *)
%o A037383 (Haskell)
%o A037383 import Data.List ((\\), nub)
%o A037383 a037383 n = a037383_list !! (n-1)
%o A037383 a037383_list = filter f [1..] where
%o A037383 f x = null $ nub (ds 3 x) \\ nub (ds 7 x)
%o A037383 ds b x = if x > 0 then d : ds b x' else [] where (x', d) = divMod x b
%o A037383 -- _Reinhard Zumkeller_, May 30 2013
%o A037383 (PARI) upto(N) = my(s7); [n|n<-[1..N], setunion(Set(digits(n, 3)), s7=Set(digits(n, 7)))==s7]; \\ _Ruud H.G. van Tol_, May 09 2024
%Y A037383 Cf. A007089, A007093.
%Y A037383 Cf. A037380, A037381, A037382, A037384, A037385, A037386.
%K A037383 nonn,base
%O A037383 1,2
%A A037383 _Clark Kimberling_