A050432 - OEIS

%I #13 Dec 17 2020 14:27:06

%S 1,1,1,1,2,1,1,1,1,2,1,1,1,1,2,2,3,1,1,2,3,2,2,1,3,2,1,1,3,1,2,2,1,3,

%T 1,1,2,3,1,2,2,3,2,1,1,3,2,2,1,1,3,1,2,1,3,1,1,2,3,2,2,2,3,3,4,2,2,3,

%U 3,3,3,3,1,2,1,3,1,1,2,2,3,2,2,3,4,3,3,2,3,2

%N Length of longest palindromic subword of (n base 4).

%H Robert Israel, <a href="/A050432/b050432.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) <= min(a(4*n+k): 0 <= k < 4). [_Reinhard Zumkeller_, Jul 31 2011]

%p LPS:= proc(L) local nL,n,i;

%p   nL:= nops(L);

%p   for n from nL to 1 by -1 do

%p     for i from 1 to nL-n+1 do

%p       if L[i..i+n-1] = ListTools:-Reverse(L[i..i+n-1]) then return n fi

%p   od od:

%p end proc:

%p seq(LPS(convert(n,base,4)),n=1..100); # _Robert Israel_, Dec 17 2020

%Y Cf. A050430, A050431, A050433.

%K nonn,base

%O 1,5

%A _Clark Kimberling_