Quick question about notation and pronunciation of indices: (i+1)st or (i+1)th?

Question

I have a somewhat silly question: What are you calling the index after the $i$th index? The $i+1$st or the $i+1$th? How do you pronounce it and how do you write it down?

I like to write $i+1$ in parentheses because otherwise the $i$ and the $1$th look too separate to me. Intuitively I would pronounce it "i-plus-first", but I'm not a native speaker.

Answer 1

Even though I'm not a native speaker, I'm pretty sure that my professor reads it as "$i+1$st". Also, I suppose it's a lot easier to pronounce this creature this way.

Answer 2

I am a native speaker, and in class, I always said “i plus oneth”, “i plus two-th”, “i plus three-eth”. And the students always laughed. My impression is that there is no standard or accepted choice between the two.