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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 10.
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%I #4 Dec 09 2015 20:17:32

%S 0,1,2,3,0,5,5,5,0,5,10,10,0,5,10,15,0,17,17,17,0,21,21,21,0,25,25,25,

%T 0,29,29,29,0,17,34,34,0,21,38,38,0,25,42,42,0,29,46,46,0,17,34,51,0,

%U 21,38,55,0,25,42,59,0,29,46,63,0,65,65,65,0,65,65,65,0,65,65,65,0,65,65,65,0,65,65,65,0,85,85

%N 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 10.

%Y Sequences related to palindromic floor and ceiling: A175298, A206913, A206914, A261423, A262038, and the large block of consecutive sequences beginning at A265509.

%K nonn,base

%O 0,3

%A _N. J. A. Sloane_, Dec 09 2015