Put another way, in 1952 and 1953 Ascari won every Championship GP he started except for France and Italy in 1953.
Indianapolis is an irrelevance - when the World Drivers' Championship was inaugurated the Americans quite rightly said that it couldn't be termed a 'World' championship without the world's greatest race. (Incidentally when Formula 1 was introduced in 1947, the organisers tried to change the Indianapolis rules to make the race compliant but under pressure from the runners of 3-litre supercharged cars, principally the Novis, they stayed with what they had that was essentially the 1938 Grand Prix rules).
And please, don't use F1 as shorthand for World Championship - they are not the same thing. Remember it has only been named the "FIA Formula 1 World Championship" since 1982. There were 30 years of World Championship history before then!