ipad a1337 wont turn on

I have some first gen iPads (A1337 - 16GB w 3G).

None of them will turn on. I can plug them in to charge with the USB cable/Adapter in a wall socket and see the slowly blinking apple, so I assume they all have a good charge after 48 hours.

When I take them to my laptop to set them up (they have been used previously but boxed up for the last year after they were wiped), there seems to be no way to turn them on at all, much less sync them or update them with iTunes.

All that happens when I attach them to my mac book pro is the slightest blink of the screen recurring appr. once per second (you don't even see this in a well lit room - I only see it when my overhead light is off and my desklamp is on low). There is just a flicker - nothing I see on screen that is recognizable.

I have tried the power button on the side, the button on the front... combinations of the two... holding them as opposed to pressing them - nothing seems to work.

How do I get them to come on so they can be updated?