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 A333770 #14 May 04 2020 13:08:53 %S A333770 1,3,9,33,88,252,737,2222,6666,19691,59095,177771,532235,1594951, %T A333770 4783874,14355341,43055034,129141921,387424783,1162332611,3486886843, %U A333770 10460406401,31381118313,94143234149,282429924282,847288882748 %N A333770 Smallest palindromic number >= 3^n. %H A333770 Robert Israel, <a href="/A333770/b333770.txt">Table of n, a(n) for n = 0..2093</a> %F A333770 a(n) = A262038(A000244(n)). - _Michel Marcus_, May 04 2020 %e A333770 a(10) = 59095, because 3^10 = 59049 and 59095 is the smallest palindromic number >= 59049. %p A333770 digrev:= proc(n) local L,i; %p A333770 L:= convert(n,base,10); %p A333770 add(L[-i]*10^(i-1),i=1..nops(L)) %p A333770 end proc: %p A333770 f:= proc(n) local d,x,y,t; %p A333770 d:= ilog10(n)+1; %p A333770 if d::even then %p A333770 x:= floor(n/10^(d/2)); %p A333770 t:= x*10^(d/2)+digrev(x); %p A333770 if t >= n then return t fi; %p A333770 (x+1)*10^(d/2)+digrev(x+1); %p A333770 else %p A333770 x:= floor(n/10^((d-1)/2)); %p A333770 t:= x*10^((d-1)/2)+digrev(floor(x/10)); %p A333770 if t >= n then return t fi; %p A333770 y:= x mod 10; %p A333770 if y < 9 then return t + 10^((d-1)/2) fi; %p A333770 x:= x+1; %p A333770 x*10^((d-1)/2)+digrev(floor(x/10)); %p A333770 fi %p A333770 end proc: %p A333770 seq(f(3^i),i=0..30); # _Robert Israel_, May 04 2020 %o A333770 (PARI) a(n) = for(k=3^n, oo, if(Vecrev(v=digits(k))==v, return(k))); %Y A333770 Cf. A000244, A002113, A262038, A333016. %K A333770 easy,nonn,base %O A333770 0,2 %A A333770 _Eder Vanzei_, Apr 04 2020