Chained arrow notation is a generalization of up-arrow notation devised by J. H. Conway and R. K. Guy. Nathan Ho and Wojowu showed that chained arrow notation terminates — that is, its output exists for all input sequences. By Bird's Proof, chained arrow notation is roughly comparable to 4-entry arrays in Jonathan Bowers' linear array notation, but is far exceeded by arrays with 5 entries or more.