T=2 icosahedral capsid is composed of 12 pentameric dimers for a total of 120 capsid proteins.
The T=2 symmetry is an nonofficial appellation, to be rigorous the capsid has a T=1 symmetry with each unit composed of a homodimer.

Icosahedric triangulation number is calculated following Caspar and Klug system (1962 PubMed)