We have heard, seen this pattern before.
( We ( ( have ( ( ( ( heard , ) seen ) ( this pattern ) ) before ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP have) (VP (VBN heard) (, ,) (VBN seen) (NP (DT this) (NN pattern)) (PP (IN before)))) (. .)))
We've never seen or heard this pattern before.
( We ( ( ( 've never ) ( ( ( seen or ) heard ) ( ( this pattern ) before ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP 've) (ADVP (RB never)) (VP (VBN seen) (CC or) (VBN heard) (ADVP (NP (DT this) (NN pattern)) (IN before)))) (. .)))