Is this a proper rendering for "$b$ is a power of 2" using TNT from Gödel, Escher, Bach In the book "Gödel, Escher, Bach" by Hofstadter introduces the system of "Typographical Number Theory". One of the exercises is to write 'b is a power of 2', I ended up coming up with the following $<(a \cdot c)=b \supset \exists a':(SS0 \cdot a')=a \land \exists c': (SS0 \cdot c')=c>$ My interpretation into English of the phrase is "$a$ and $c$ being factors of $b$ implies that both and $a$ and $c$ are even" which I believe only holds true for $b$ that are powers of 2. Is this a valid way of writing 'b is a power of 2' in the system, and if it is/isn't how can I be sure.

Make sure to universally quantify the $a$ and $c$. And yes, then your formula works since then it implies that $b$ has no factors other than $2$
