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 A331173 #7 Jan 12 2020 23:50:56
%S A331173 0,1,2,3,4,5,6,5,8,9,10,11,12,13,14,15,16,17,18,11,20,15,14,23,24,17,
%T A331173 26,27,28,29,30,31,32,33,34,35,36,31,38,39,40,41,42,43,44,45,34,47,48,
%U A331173 43,50,51,52,53,54,29,56,33,38,59,60,47,62,45,32,59,42,41,68,69,50,71,72,35,62,51,44,71,78,53,80,81
%N A331173 a(n) = min(n, A263273(n)), where A263273 is bijective base-3 reverse.
%C A331173 For all i, j:
%C A331173 a(i) = a(j) => A290094(i) = A290094(j).
%C A331173 For all i, j > 0:
%C A331173 a(i) = a(j) => A007949(i) = A007949(j).
%H A331173 Antti Karttunen, <a href="/A331173/b331173.txt">Table of n, a(n) for n = 0..59048</a>
%o A331173 (PARI)
%o A331173 A030102(n) = { my(r=[n%3]); while(0<n\=3, r=concat(n%3, r)); subst(Polrev(r),x,3); } \\ After code in A030102.
%o A331173 A263273 = n -> if(!n,n,A030102(n/(3^valuation(n,3))) * (3^valuation(n, 3)));
%o A331173 A331173(n) = min(n, A263273(n));
%Y A331173 Cf. A007949, A030102, A263273, A290094.
%Y A331173 Cf. also A330740, A331166.
%K A331173 nonn,base
%O A331173 0,3
%A A331173 _Antti Karttunen_, Jan 12 2020