The sentence from Euler's De Serie Lambertina I'm working on now has the following form:
Praesenti autem forma hanc seriem exhibere est visum, ut litterae A et B inter se permutabiles evaderent, ita ut, quicquid de altera fuerit observatum, etiam de altera valeat.
I've translated this (to the best of my ability) as:
With the present form, however, this series is seen to show, as the letters A and B may come out interchangeable between themselves, in such a way that, whatever may be observed from one, may also be valid for the other.
Is "est visum" the perfect passive? Then, if that clause is correct, it seems like it's left dangling. Then, why "evaderent" (evado, to avoid, keep away from, come out/go out) and how should such a phrase as "inter se [adjective] evaderent" be translated?