Bb Major 7#11, 3rd inversion (A in the bass)
Also written as Bbmaj7#11/A.
Notes, from the bass up
A (bass)EA#DE#
The same notes as Bb Major 7#11 (A, E, A#, D and E#), rearranged so A is the lowest note. Use it to move between chords with smaller jumps across the keyboard.