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 A355062 #19 Jul 01 2025 09:02:09
%S A355062 4,8,9,16,25,27,36,49,125,128,144,169,225,256,289,1156,1225,1369,1444,
%T A355062 4489,6889,11236,11449,13456,13689,27889,33489,111556,112225,113569,
%U A355062 134689,146689,344569,444889,2666689,2778889,11115556,11122225,11135569,11336689
%N A355062 Perfect powers whose digits are in nondecreasing order.
%C A355062 I.e., numbers of the form b^k with b > 1 and k > 1 in whose base-10 expansion no digit is less than the previous digit.
%C A355062 Includes infinite subsequences such as {16, 1156, 111556, 11115556, ...} and {25, 1225, 112225, 11122225, ...}, so the sequence is infinite.
%H A355062 Michael S. Branicky, <a href="/A355062/b355062.txt">Table of n, a(n) for n = 1..261</a>
%t A355062 perfectPowerQ[n_] := GCD @@ FactorInteger[n][[All, 2]] > 1; (* A001597 *) Select[Range[10^6], perfectPowerQ[#] && Min[Differences[IntegerDigits[#]]]>-1 &] (* _Stefano Spezia_, Jul 01 2025 *)
%o A355062 (Python)
%o A355062 from sympy import perfect_power as pp
%o A355062 from itertools import count, islice, combinations_with_replacement as mc
%o A355062 def agen():
%o A355062 for d in count(1):
%o A355062 ni = (int("".join(m)) for m in mc("123456789", d))
%o A355062 yield from filter(pp, ni)
%o A355062 print(list(islice(agen(), 40))) # _Michael S. Branicky_, Jun 16 2022
%o A355062 (PARI) isok(m) = if (ispower(m), my(d=digits(m)); (d == vecsort(d))); \\ _Michel Marcus_, Jun 18 2022
%Y A355062 Cf. A001597, A009994, A355060.
%K A355062 nonn,base
%O A355062 1,1
%A A355062 _Jon E. Schoenfield_, Jun 16 2022