f57v

[ThomasCoon]

This sequence is also mentioned by Mary D'Imperio  in her 1978 work:

An interesting bit of evidence for the identity of "p" and "f" (and thus, by analogy, the other pair "t" and "k" as well) may be seen on folio 57r, where a sequence of seventeen symbols is repeated four times around a circular band. It is so rare to find any sequence in the Voynich manuscript repeating all or some portion of itself that this example is almost unique. Figure 24 shows the four repeated segments arranged in parallel; in two instances, the symbol "f" with only one loop occurs in the ninth place, while in the other two, we see "p" with two clear loops in the corresponding position. Since all the other symbols appear identical, the conclusion seems inescapable that the single- and double-looped forms are functionally the same.

For some reason she says 57r instead of 57v, but it's clear what page she means.