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 A265514 #4 Dec 09 2015 20:22:29 %S A265514 0,1,2,3,0,11,11,11,0,11,22,22,0,11,22,33,0,101,101,101,0,111,111,111, %T A265514 0,121,121,121,0,131,131,131,0,101,202,202,0,111,212,212,0,121,222, %U A265514 222,0,131,232,232,0,101,202,303,0,111,212,313,0,121,222,323,0,131,232,333,0,1001,1001,1001,0,1001,1001,1001,0 %N A265514 a(n) = largest base-4 palindrome m <= n such that every base-4 digit of m is <= the corresponding digit of n; m is written in base 4. %Y A265514 Sequences related to palindromic floor and ceiling: A175298, A206913, A206914, A261423, A262038, and the large block of consecutive sequences beginning at A265509. %K A265514 nonn,base %O A265514 0,3 %A A265514 _N. J. A. Sloane_, Dec 09 2015