Animate object every second according to set values?

OK, so this has been driving me nuts for most of the morning, and I can't seem to figure it out.  (But my code writing from scratch is scrappy, at the best of times!)

I have three shape layers that need to change size every second (or possibly at another set interval), but I have the sizes defined.  It's an animated chart, with each second marking a month, but for thea animation to go smoothly.

I have found a handful of expressions, but can't seem to get any of them to work as I need them.  I've tried this:

linear(time, 0, 1,  content("mycircle").size*1,  content("mycircle").size*1.3);

Which works for one second, but can't seem to get it to size for two seconds like this:

linear(time, 0, 1,  content("mycircle").size*1,  content("mycircle").size*1.3);
linear(time, 1, 2,  content("mycircle").size*1.3,  content("mycircle").size*1.4);

And I've tried this, which like the one above, only reads the last value in the script:

content("mycircle").size.valueAtTime(time + 1)*1;
content("mycircle").size.valueAtTime(time + 2)*1.3;
content("mycircle").size.valueAtTime(time + 3)*1.4;

I thought it might be possible to do with an array, somehow, but can't figure out how.

If "mycircle" size has to change every second for each month, as below:

What would be the best expression to do that?  Any help at all would be greatly appreciated!

I'm fairly new to expressions, too.  Please be gentle.