This is related to the following questions, 1, 2.
In many papers in mathematics, I often see the following constructions.
Similar to [1], we have that 2+ax = 3y.
Similar to Equation 2.3, we note that ax = by for non-negative integers a and b.
By straightforward calculations similar to Equation 2.2, p=np.
To be clear, the authors usually mean to say a lengthy calculation is identical to the procedure used to arrive at an equation earlier in the paper in the case of the second and third example, or in a cited source in the first example.
After reading the aforementioned related questions and related discussion elsewhere, I still do not understand whether or not these examples should be written as "similar" or "similarly".
Based on 1, I suspect that the correct choice is similarly, however I am experiencing cognitive dissonance because I rarely see these sentences written like this. After consulting with others I consider fairly well versed in English, they all agree that "Similarly" sounds strange in all three of these contexts too.
The argument I am faced with is whether we should use the adverb, similarly, by essentially implicitly encapsulating the entire process to arrive at a new equation as the verb; or whether we should use the adjective, similar, to suggest that the equation or citation are similar to our equation, but leave us with the ambiguity illustrated in user curious-proofreader's Tokyo example found in 2.