PKCS12 key derivation
Yes, it should be Ai, or more exactly A_i denoting subscript. Note that i (the chunk subscript) is not I (the salted password input). I submitted this to rfc-editor in Feb (see https://security.stackexchange.com/questions/112627/what-password-based-key-derivation-does-pkcs-12-use) and they said they were going to fix it; I guess it got lost.

For confirmation you can see the source document from RSAlabs-now-EMC linked there, at least as long as Dell doesn't start mangling the EMC website(s) the way EMC for years mangled the RSAlabs website.

And that PKCS12 PBE is still used, even though PBES2/PBKDF2 from PKCS5v2 is now recommended (and other options like bcrypt, scrypt, Argon2 even more).