Such were the locksmith’s thoughts when first seated in the snug corner, […] — (Charles Dickens, Barnaby Rudge )
This is referred to as linear growth because the number of recursive calls is directly proportional to the value of the argument provided when the function is first called. — (Ben Stephenson, The Python Workbook , (2nde édition), Springer, 2019, lêmbëtï 131)