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 A321539 #20 Aug 10 2023 15:35:35
%S A321539 1,3,9,72,81,432,972,8721,6651,98631,99540,777411,544311,9543321,
%T A321539 9987642,98744310,76443210,964321110,988744320,7666422111,8876444310,
%U A321539 65433321000,99865331100,98877443211,988654432221,988876444320,9888655432221
%N A321539 3^n with digits rearranged into nonincreasing order.
%H A321539 Paolo Xausa, <a href="/A321539/b321539.txt">Table of n, a(n) for n = 0..1000</a>
%F A321539 a(n) = A004186(A000244(n)). - _Michel Marcus_, Nov 10 2022
%t A321539 A321539[n_]:=FromDigits[ReverseSort[IntegerDigits[3^n]]];Array[A321539,40,0] (* _Paolo Xausa_, Aug 10 2023 *)
%o A321539 (Python)
%o A321539 def A321539(n): return int(''.join(sorted(str(3**n),reverse=True))) # _Chai Wah Wu_, Nov 10 2022
%Y A321539 The following are parallel families: A000079 (2^n), A004094 (2^n reversed), A028909 (2^n sorted up), A028910 (2^n sorted down), A036447 (double and reverse), A057615 (double and sort up), A263451 (double and sort down); A000244 (3^n), A004167 (3^n reversed), A321540 (3^n sorted up), A321539 (3^n sorted down), A163632 (triple and reverse), A321542 (triple and sort up), A321541 (triple and sort down).
%Y A321539 Cf. A004186.
%K A321539 nonn,base
%O A321539 0,2
%A A321539 _N. J. A. Sloane_, Nov 19 2018