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 A342942 #18 Jun 12 2025 20:55:25
%S A342942 12,13,34,48,67,102,123,146,408,449,696,698,942,1002,1030,1234,1367,
%T A342942 4008,5221,6948,10002,10030,10203,10406,12124,12345,12568,40008,40409,
%U A342942 52280,61732,94206,100002,102214,106625,121024,123456,400008,637832,1000002,1000300,1002003
%N A342942 Numbers whose palindromization is a perfect power.
%C A342942 Palindromization is the function that extends the string representation of a number into a palindrome.
%C A342942 Even palindromization is the concatenation of a number and its reversal. Odd palindromization excludes the first digit of the reversal.
%H A342942 Chai Wah Wu, <a href="/A342942/b342942.txt">Table of n, a(n) for n = 1..1997</a> (terms 1..100 from Michel Marcus)
%e A342942 12 is a term because 121 is a square.
%e A342942 13 is a term because 1331 is a cube.
%t A342942 Select[Range[10,50000],Or@@(GCD@@Last/@FactorInteger@#>1&/@FromDigits/@(Join[a,Reverse@#]&/@{a=IntegerDigits@#,Most@a}))&] (* _Giorgos Kalogeropoulos_, Mar 30 2021 *)
%o A342942 (PARI) rev(x) = strjoin(Vecrev(Str(x)));
%o A342942 isok(m) = ispower(eval(Str(m, rev(m)))) || ispower(eval(Str(m, rev(m\10))));
%Y A342942 Cf. A075786, A076443, A001597, A002113, A342803.
%K A342942 nonn,base
%O A342942 1,1
%A A342942 _Michel Marcus_, Mar 30 2021