[1.] Analytic a posteriori judgments cannot arise, since there is never any need to appeal to experience in support of a purely explicative assertion.
[2.] Analytic a posteriori claims are claims that are tautologically true, but can only be understood through empiricism. Walter Block has an excellent example of such a truth.
Although there is some question about this in philosophical circles, one way to characterize the elements in this set is in terms of the ways in which we come to learn language. For example, “We shall use language in such a way that ‘rouge’ in French will translate to ‘red’ in English.” We learn this through experience, but to say “[3.] Rouge equals red” is an analytic statement. For A, the analytic a posteriori, we can learn each of the words in this sentence through experience (in an a posteriori manner), and yet the meaning of it is tautological. [This link was broken when I tried it on 2016/3/9.]
I agree, and so do not challenge here, that 3 is analytic; as the etymology of 'analytic' suggests, the meaning of the sentence must be 'loosened up' from the sentence that itself must be 'loosened up' by examining each word.
Hereafter, I use the (Proto-Indo-European root) reudh to mean the colour red itself (which transcends all languages) and to disambiguate it from the English noun 'red'.
But as 1 and 2 appear to contradict each other, I question whether 3 is a posteriori. Why need I any visual experience of reudh, or any colour, to understand 3? If, never having seen reudh, I am told that 'rouge' means the exact same thing as 'red', then I will have understood the equivalence of the nouns 'red' and 'rouge' (though I still will not know how reubh appears).