Interpolating between the values in a list - Refining/ Filling a list

Hey guys,

I've been trying to do a seemingly easy thing for the last hours and I'm almost there - but i can't wrap my head around why it's not working the way i expect it to. It's probably a timing issue but there's so much going on at the same time I can't figure it out myself, so maybe you could help.

The idea of this patch is:

I have a list (eg. [1 2 3 4])

I want to double the size of the list and fill the spaces between the values with interpolations between them like this(in my specific case i want to "refine" a multisliders look with this later on):

[1 1.5 2 2.5 3 3.5 4]

Sometimes i get it to work by changing the lookup number manually but the one button solution never works.

Any ideas?

Or maybe there's a better object to do this?