3,4,2,1. Because that's what they did on Lancasters.....
Watched the start up of a B-52 once - levers all over the place as 2 pilots started a seemingly random selection of the 8 engines each!
Original V-bombers could start all 4 simultaneously, put all the gennies on and switch all the electro-hydraulic PFCUs on - all at the same time!