4-3a

#g2 f1 % almost decomposable bravais-group
4	% generator
 -1 1 0 0
  0 1 0 0
  0 0 1 0
  0 0 0 1
4	% generator
  0  0 -1  5
 -1  0 -2 10
  0 -1 -3 15
  0  0 -1  4
4	% invariant form
 10 -5   0   0
 -5 10  -5   0
  0 -5  10 -25
  0  0 -25 100
2^4  * 3^1  * 5^1   = 240 % order of the group