Trying out J!
» jconsole comb=: [:;(,.&.><@:>:@;\.)^:(i.@>:@-~`[`(1:<@i.@{.~<:@-,2:)) 2 comb 3 0 1 0 2 1 2
Reading answer like this makes me think I should have spent more times with J when I first discovered it years ago.