pairSequence :: [a] -> [(a,a)]
pairSequence (a:b:xs) = (a,b) : pairSequence xs
pairSequence :: [a] -> [(a,a)]
pairSequence (a:b:xs) = (a,b) : pairSequence xs
pairSequence (a:b:xs) = (a,b) : pairSequence xs