"an element's ordinal (subscript) equals the number of elements preceding it in the sequence." That is going to make the "the 2nd item is number 1" thing SO mu

"an element's ordinal (subscript) equals the number of elements preceding it in the sequence." That is going to make the "the 2nd item is number 1" thing SO much easier to explain when teaching. Thanks! (And it's good to have the rest of the reasoning there to answer the particularly curious students...) Definitely falls into the "wish I'd thought of that" and "wish I'd heard someone say it that way 5 years ago" camps.