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 A043038 #15 Aug 03 2014 14:31:47
%S A043038 3,33,303,313,323,333,343,353,363,373,383,393,3003,3113,3223,3333,
%T A043038 3443,3553,3663,3773,3883,3993,30003,30103,30203,30303,30403,30503,
%U A043038 30603,30703,30803,30903,31013,31113,31213,31313,31413,31513,31613,31713,31813,31913
%N A043038 Base-10 palindromes that starts with 3.
%C A043038 Subsequence of A002113 (palindromic numbers). Union of A222725 (palindromic primes starting with a digit 3) and A222726 (palindromic composite numbers starting with a digit 3). - _Jaroslav Krizek_, Mar 12 2013
%H A043038 Jaroslav Krizek, <a href="/A043038/b043038.txt">Table of n, a(n) for n = 1..2222</a>
%t A043038 okQ[n_]:=Module[{idn=IntegerDigits[n]}, First[idn]==3 && n==FromDigits[Reverse[idn]]]; Select[Range[40000],okQ] (* _Harvey P. Dale_, Jan 14 2011 *)
%K A043038 nonn,base
%O A043038 1,1
%A A043038 _Clark Kimberling_