Dude -

This question's a little hard to interpret.. are you talking about an extension of your triplet pattern which starts with a tap and ends with a tap, or doing a four-note pattern involving a single tap?

Assuming the latter, the simplist four note patterns involving a single tap are the same as your triplet pattern, only with an extra hammer or pull-off.

if thought in terms of sequence of technique - they are

Tap (eg. high E string, 12th fret high E)
Pull (pull tapping finger off, sound A)
Hammer (from A (index) to C (pinky))
Pull (back to A)

..or using the same notes

Tap (12th fret E)
Pull (pull off to pinky on C)
Pull (pull off to index finger on A)
Hammer (hammer back to C with pinky)

Peace -
Damos