Applying the same procedure to any positive integer <math>n\!</math> produces an expression called the ''doubly recursive factorization'' of <math>n\!</math> and notated as <math>\operatorname{drf}(n).\!</math>
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Applying the same procedure to any positive integer <math>n\!</math> produces an expression called the ''doubly recursive factorization'' of <math>n.\!</math> For ease of discussion, it serves to call this the ''drift'' of <math>n\!</math> and to notate the corresponding mapping from numbers to expressions as <math>\operatorname{drift}(n).\!</math>