"One won't be much global economic impact. Three in one country will ripple out for years. Any more than that will change things forever."
One would cause oil to shoot up over the $100 barrel mark overnight and oil drives everything else. Real bad news is bad for stocks, one or three nukes at the same time is about the same effect to our markets.
The difference is that three would put any modern country down for a long time. One would cause disruption for a time. Difference is how long. I wouldn't worry about $100 a barrel since there will be rationing as well as martial law.