The Bender-Dunne basis operators,
T−m,n=2−n∑k=0n(kn)qkp−mqn−kT−m,n=2−n∑k=0nnkqkp−mqn−k where
qq and
pp are the position and momentum operators, respectively, are formal integral operators in position representation in the entire real line
RR for positive integers n and m. We show, by explicit construction of a dense domain, that the operators
T−m,nT−m,n's are densely defined operators in the Hilbert space
L2(R)L2(R).