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A319387 Smallest palindrome p such that n-p is again a palindrome, or n if no such p exists.

%I A319387 #20 Sep 19 2018 02:58:23
%S A319387 0,0,0,0,0,0,0,0,0,0,1,0,1,2,3,4,5,6,7,8,9,21,0,1,2,3,4,5,6,7,8,9,32,
%T A319387 0,1,2,3,4,5,6,7,8,9,43,0,1,2,3,4,5,6,7,8,9,54,0,1,2,3,4,5,6,7,8,9,65,
%U A319387 0,1,2,3,4,5,6,7,8,9,76,0,1,2,3,4,5,6,7,8,9,87,0,1,2,3,4,5,6,7,8,9,98,0
%N A319387 Smallest palindrome p such that n-p is again a palindrome, or n if no such p exists.
%C A319387 a(n) = n if and only if A262087(n) = 0.
%H A319387 Robert Israel, <a href="/A319387/b319387.txt">Table of n, a(n) for n = 0..10000</a>
%e A319387 a(11) = 0 because 11 = 11 + 0, so 0 is the smallest palindrome in any partitioning of 11 as a sum of two palindromes.
%e A319387 a(21) = 21 because 21 cannot be written as a sum of two palindromes.
%p A319387 isP := k -> StringTools[IsPalindrome](convert(k,string)):
%p A319387 a := NULL:
%p A319387 for n from 0 to 99 do
%p A319387    an := n:
%p A319387    for k from 0 to n/2 do
%p A319387       if isP(k) and isP(n-k) then an := min(an,k) end if
%p A319387    end do:
%p A319387    a := a,an
%p A319387 end do:
%p A319387 a;
%Y A319387 Cf. A002113, A035137, A260254, A262087.
%K A319387 nonn,base,look
%O A319387 0,14
%A A319387 _Markus Sigg_, Sep 18 2018