This is likely to be shut down so fast, but it looks like Nintendo's first attempt at Cross Buy with OlliOlli is letting you get it on Wii U and then share it with any registered 3DS
I'm not in a position to test this at the moment, but Nintendo Life has, and says it works after buying OlliOlli and downloading it to three separate 3DS. All you have to do is register multiple 3DS Nintendo Network IDs on the Wii U you buy the game on. You'll then be able to download the game on any of the registered consoles.
It's almost certainly a glitch, rather than a feature so expect it be gone by the time you read this...
[Nintendo's Implementation of Cross-Buy is Surprisingly Generous - Nintendo Life]