A 13th chord
A13 chord for piano presented by keyboard diagrams.
Explanation: The A thirteenth is a seven-note chord. Due to practical circumstances, some notes (as a suggestion fifth, ninth, and eleventh) are omitted and the chord is played inverted, see second diagram. The chord is sometimes played with both hands. The chord is often abbreviated as A13.
Theory: The A thirteenth chord is constructed by adding a third to an eleventh chord.
Notes: A - C# - E - G - B - D - F#