Simplify the implementation of sequence.
Simplify the implementation of sequence.

zeryx/thrust,arnabgho/thrust,xiongzhanblake/thrust,andrewcorrigan/thrust-multi-permutation-iterator,jaredhoberock/thrust,jaredhoberock/thrust,marksantos/thrust,zhenglaizhang/thrust,marksantos/thrust,zeryx/thrust,mohamed-ali/thrust,GrimDerp/thrust,xiongzhanblake/thrust_src,xiongzhanblake/thrust,Ricardo666666/thrust,thvasilo/thrust,Ricardo666666/thrust,raygit/thrust,jaredhoberock/thrust,marksantos/thrust,sdalton1/thrust,zeryx/thrust,zhenglaizhang/thrust,arnabgho/thrust,sdalton1/thrust,sarvex/thrust,egaburov/thrust,jaredhoberock/thrust,dachziegel/thrust,thrust/thrust,thrust/thrust,GrimDerp/thrust,egaburov/thrust,arnabgho/thrust,dachziegel/thrust,GrimDerp/thrust,raygit/thrust,egaburov/thrust,mohamed-ali/thrust,thrust/thrust,xiongzhanblake/thrust,sarvex/thrust,sdalton1/thrust,raygit/thrust,Ricardo666666/thrust,andrewcorrigan/thrust-multi-permutation-iterator,thvasilo/thrust,mohamed-ali/thrust,sarvex/thrust,dachziegel/thrust,zhenglaizhang/thrust,thrust/thrust,xiongzhanblake/thrust_src,jaredhoberock/thrust,andrewcorrigan/thrust-multi-permutation-iterator,thrust/thrust,thvasilo/thrust,xiongzhanblake/thrust_src