What aircraft has this pattern of white strobe lights? Just two nights ago, my brother and I noticed a weird flashing light in the night sky out in the countryside. 
We regularly observe by naked eye aircraft flying by,  as well as satellites,  and this was not like anything we'd seen before. 

It was only white light (no red, no green) , with the following sequence:

 *            _______          _______


Flash   &lt;-1sec->  strong light  &lt;-1sec->   dim light

The lines above the second and third lights attempt to show the fact that they faded gradually, while the first flash was like a camera flash, sudden and strong. 

Every 3 seconds the cycle repeated.
The source of the lights seemed to be the same, i.e the same strobe light. Besides, the aircraft was pretty far away or small: with binoculars, it wasn't possible to discern any other strobe lights or a structure of any kind. 

We first noticed the light above Ursa Major, it moved towards Cassiopeia and gradually faded away either because it moved away from us or because of the strong moonlight of that night.
Twenty cycles per minute means it wasn't an FAA-approved aircraft, so it probably wasn't manned, or even a weather balloon.

Satellites need no anticollision lights.

The bright strobe combined with the longer fading lights suggests something homebuilt.  The light may have been adapted from consumer bicycle lights, which have quite a variety of patterns.  Professional lights such as Whelen's models prefer flickering to fading, for both efficiency and visibility.