The projective symplectic group 
is the group obtained from
the symplectic group 
on factoring by the scalar matrices contained in that group.
is simple except for
 |  |  |
(1)
|
 |  |  |
(2)
|
 |  |  |
(3)
|
so it is given the simpler name 
, with 
.
Projective Symplectic Group
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References
Conway, J. H.; Curtis, R. T.; Norton, S. P.; Parker, R. A.; and Wilson, R. A. "The Groups
and 
." §2.3 in Atlas
of Finite Groups: Maximal Subgroups and Ordinary Characters for Simple Groups.
Oxford, England: Clarendon Press, pp. x-xi, 1985.Referenced on Wolfram|Alpha
Projective Symplectic GroupCite this as:
Weisstein, Eric W. "Projective Symplectic Group." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ProjectiveSymplecticGroup.html