How to calculate even-money odds in french roulette?

[codekiddy]

Hello,
I'm working on statistics and need someone to say "agree" with my formula.
I hope you are good at matematics...

So my formula (which is correct for american and european roulette) is:
Ratio + (2 + 38 % Nums) / betType   (american)
Ratio + (38 % Nums) / betType   (european)

where:
ratio = payout (1 / betType * (36 - betType) )
Nums = number of fields on roulette table (37 or 38)
betType = how many fields does bet cover( 2 for split bet ...)

but I'm not sure how to calculate it for french roulette 
French roulette has "la partage" rule and I have to find odds for even-money bets.
(non even-money bet odds are the same as european roulette ofcourse)

how do I do that?

thanks alot.

PS
If I find a formula my self I'll post it here of course as soon as possible to finish the thread.