Keep your mind sharp!

Probably all of us are having a rough time.
Spending many hours indoors, worrying about what will happen, not being able to meet with friends and family...it sucks. 
I am too working from home right now in light of the (not so) new regulations and guidelines, and I am not as active as I am used to or would like to be.
I actually have a lot of cool stuff already planned (like more Sudoku variants, a somewhat systematic analysis of Raven matrices style puzzles and something else completely original that you've probably never seen anywhere else).
Unfortunately due to the current ongoing Corona saga and some other personal stuff, I'll be slow with actually finalizing everything (having an idea is one thing, actually putting it into a coherent text that I am happy to present as my own and creating the necessary visuals to get my point across is another).
Nevertheless, I thought this might also be a good opportunity to help you guys (and myself) to stay sharp and entertain ourselves while being stuck at home or trying to figure out what to do without as many social interactions if any.
Nothing really beats a deep conversation as stimulation for your brain, but I hope this few number and visual series-style puzzles can be a close second:

Can you figure out what number should come next?
3,3,6,5,12,7,___,___
7,36,148,594,___
2,3,11,92,1116,___

How about these letters?
b,c,d,d,f,e,h,f,___,___
a,y,z,x,y,w,___,___,___
b,d,h,p,f,___,___

Here are some nice shapes, can you figure out what's the next one in each series?

And one last challenge; Can you figure out what configuration should be on top, even though you are not able to see all the steps?

That's all for now! I hope you liked this quick update, I hope I helped even a little bit to reduce your daily boredom or at least that I was able to distract your mind from all the chaos and uncertainty we all have to endure.
Be safe, wash your hands, use common sense and your critical thinking and keep that cortex active!