Hello,
I'm having problems with a mathematical equation to get center position.

I'm making a game in VB6 which involves cards to be generated in center of some offset I pick..

I put a few cards in microsoft paint program to see how the X coordinate changes as the spread out more and more seems to exactly 30 pixels apart.. but the thing is the cards have to also overlap other cards meaning at first I thought it was possible without re-drawing everything just keep adding cards and they would sort out and center. But it seems the only way is to provide the size of how much cards you want to display then it's possible to center those.. and still I cannot do that.

Here is the stats I gathered
X:35 = 1 CARD CENTERED.
X:20 X:50 = 2 CARDS CENTED
X:5 X:35 X: 65 = 3 CARDS CENTERED
X:-10 X:20 X:50 X:80 = 4 CARDS CENTERED.

figured they are 30 SUBTRACTED from previous card.

Now i'm trying to write a function that returns X for next card Position.

Code:
function getCenterOffset(cardPos as integer, numCards as integer)
//all I got at the moment.
getCenterOffset = 0
end function
honestly I'm just looking for the equation..

I been fooling around with the math and came up with this..

curPosition, maxCards
0 and maxCards = 4

20+15x0=20 [-30] = -10
20+15x2=50 [-30] = 20
20+15x4=80 [-30] = 50
20+15x6=110 [-30] = 80

curPosition, maxCards
0 and maxCards = 3

20+15x1=35 [-30] = 5
20+15x3=65 [-30] = 35
20+15x5=95 [-30] = 65

curPosition, maxCards
0 and maxCards = 2

20+15x2=50 [-30] = 20
20+15x4=80 [-30] = 50

curPosition, maxCards
0 and maxCards = 1

20+15x3=65 [-30] = 35


As you can see from my math above I got to something.. when maxCards is odd the multipiler is odd and even is even..
Also the last card position is maxCards+2 from my equations but i dont know what else to do to make it a algorithm


note maxCards 4 is not the limit it could go very high maybe up to 30.. and i don't want them in a huge array or loops i know its possible with good old math equation.


So yah i'm stumped can someone help me out thanks