I've put together a chart showing down, distance and yards gained against Seattle on every pass play of at least 15 yards this season. It's a fairly long chart, so you'll have to click the little "read more" link to see the thing. Fourteen of these plays have occurred on first down, 11 on second down and eight on third down. The average play would gain 25.4 yards on second-and-10 (actually 1.8-and-9.7, if such a down-and-distance existed).
NOTE: I have added a chart showing similar plays by Seattle's offense this season. It is a slightly shorter list.
In reading the summary chart at top, note that the middle three columns show yards gained on the play. So, for example, there have been six first-down pass plays that gained between 20 and 29 yards.
We can also sort these 15-plus pass plays by opponent: Detroit 5, Arizona 3, Giants 7, Chicago 5, St. Louis 7, Minnesota 6.
If we narrow it to 20-plus pass plays, the breakdown goes like this: Detroit 3, Arizona 1, Giants 4, Chicago 3, St. Louis 5 and Minnesota 2.
CHARTS ON LEFT SHOWS OPPONENTS' BIG PASS PLAYS VS. SEATTLE
CHARTS AT RIGHT SHOW SEATTLE'S BIG PASS PLAYS