ABSTRACT
Beginning on page 6 of the Coss , Jacob found an explanation of series —progressions. He carefully talked himself through the explanation: “All right. First Rudolph presents arithmetic series, in which I should always add the same amount-the common diff erence-as I move from one term to the next. His fi rst series is the fi rst seven counting numbers-1, 2, 3, 4, 5, 6, 7-in this case I simply add one for each new term. at’s easy.
