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{\bf Murray Elder }
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{\bf Permutations Generated by a Stack of Depth 2 and an Infinite Stack in Series}
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We prove that the set of permutations generated by a stack of depth
two and an infinite stack in series has a basis (defining set of
forbidden patterns) consisting of 20 permutations of length 5, 6, 7
and 8. We prove this via a ``canonical'' generating algorithm.
\bye