  Consider the operation of adding the same number of identical digits to the
left and to the right of a number n. In OEIS sequence A090287, it was
conjectured that this operation will not produce a prime if and only if n is a
palindrome with an even number of digits. We show that this conjecture is false
by showing that this property also holds for n=231, n=420, and an infinite
number of other values of n.
