Zeta2 denotes Zeta[2].
Zeta2
Zeta[2]
Overview, SimplifyPolyLog.
ζ(2)\zeta (2)ζ(2)
N[Zeta2]
1.644931.644931.64493
SimplifyPolyLog[Pi^2]
6ζ(2)6 \zeta (2)6ζ(2)
Conjugate[Zeta2]