A sus4/A#
The A sus4 chord consists of the A (Perfect unison), D (Perfect fourth) and E (Perfect fifth) notes, with A# as the bass note.

How to play the A sus4/A# chord
- Play A# as the lowest bass note in the left hand
- Find A (Root) on the piano keyboard
- Add D (Perfect fourth) — 5 semitones above A
- Add E (Perfect fifth) — 7 semitones above A
- Press all 4 notes simultaneously to sound the A sus4/A# chord