sequences.extras: use either?.
sequences.extras: use either?.

bpollack/factor,nicolas-p/factor,dch/factor,factor/factor,bpollack/factor,sarvex/factor-lang,bjourne/factor,bjourne/factor,AlexIljin/factor,AlexIljin/factor,nicolas-p/factor,AlexIljin/factor,slavapestov/factor,tgunr/factor,factor/factor,AlexIljin/factor,slavapestov/factor,bjourne/factor,nicolas-p/factor,slavapestov/factor,bpollack/factor,slavapestov/factor,factor/factor,mrjbq7/factor,dch/factor,slavapestov/factor,tgunr/factor,sarvex/factor-lang,AlexIljin/factor,sarvex/factor-lang,dch/factor,bpollack/factor,mrjbq7/factor,bjourne/factor,bpollack/factor,bpollack/factor,mrjbq7/factor,mrjbq7/factor,slavapestov/factor,dch/factor,bjourne/factor,sarvex/factor-lang,factor/factor,nicolas-p/factor,dch/factor,nicolas-p/factor,mrjbq7/factor,nicolas-p/factor,AlexIljin/factor,factor/factor,bjourne/factor,bpollack/factor,sarvex/factor-lang,sarvex/factor-lang,dch/factor,bjourne/factor,slavapestov/factor,tgunr/factor,sarvex/factor-lang,AlexIljin/factor,nicolas-p/factor,factor/factor,tgunr/factor,tgunr/factor,mrjbq7/factor,tgunr/factor