Puzzle #100: HASTA LA VISTA!

Of the letters of the alphabet that occur in “HASTA LA VISTA!”, all but one have something in common. What is it, and which letter is the oddball? (Consider the capital forms of the letters only.)

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, May 6, 2015 at noon Pacific Time. I will post the answer shortly after.