If it's a real old friend (or someone I just click with that well) where akward silences aren't real akward and we can chill, one on on isn't an issue. One of my friends I can think of who's even a bit on the periphery right now I usually call him or get a call from him, stop over after school (usually like 9:30 or 10 at night once his girlfriend goes to work and the kids are in bed) and we'll usually watch a movie, some NWO, or whatever. Then again in his case I've also known the guy since I was in 11th grade.
As for larger groups though, I kinda prefer 3 or 4. 4 is especially nice because I can usually get by with just adding bits of my own energy, holding off on the comments till I have something pretty glib or funny, and it works out pretty well because no one person has to put much more than 25% in, some people naturally being extroverts end up putting in 30 or 35% just in fulfilling their own needs, and I usually only get stuck putting in 10 or 15% which I'm more than happy with when we're just chillin and it's all small talk.
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The loneliest part of life: it's not just that no one is on your cloud, few can even see your cloud.