It is a fairly common mix up. The Douglas Invader was designated the A-26 as well as the B-26.
For the anoraks
Element of deliberate confusion
Martin was the B26
Douglas started life as the A26
Martin went out of service
Douglas became the B26 (must have caused problems with stuff still sitting in stores)
In the late 50's/early 60's Thailand didn't want US bombers based there but were happy with attack aircraft
Douglas went back to being the A26.