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 A043040 #30 Jul 07 2025 04:09:10
%S A043040 0,5,55,505,515,525,535,545,555,565,575,585,595,5005,5115,5225,5335,
%T A043040 5445,5555,5665,5775,5885,5995,50005,50105,50205,50305,50405,50505,
%U A043040 50605,50705,50805,50905,51015,51115,51215,51315,51415,51515,51615,51715,51815,51915
%N A043040 Numbers that are palindromic and divisible by 5.
%C A043040 Or, 0 and numbers that are palindromic and begin with 5.
%H A043040 Jaroslav Krizek, <a href="/A043040/b043040.txt">Table of n, a(n) for n = 1..2223</a>
%t A043040 palQ[n_Integer, base_Integer] := Module[{idn = IntegerDigits[n, base]}, idn == Reverse[idn]];
%t A043040 Join[{0},Select[Range[5,100000,5], IntegerDigits[#][[1]] == 5 && palQ[#, 10] &]] (* _T. D. Noe_, Mar 12 2013 *)
%t A043040 Select[5*Range[0,11000],IntegerDigits[#]==Reverse[IntegerDigits[#]]&] (* _Harvey P. Dale_, Nov 29 2015 *)
%Y A043040 Intersection of A002113 and A008587.
%Y A043040 Cf. A029951, A045638, A045639, A045641, A045642, A045643, A045644, A083852.
%K A043040 nonn,base
%O A043040 1,2
%A A043040 _Clark Kimberling_
%E A043040 Edited to include a(1) = 0 by _Paolo Xausa_, Jul 07 2025