On a subgroup of the affine Weyl group<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="$\tilde{C}_4$" id="E1"><mml:msub><mml:mover accent="true"><mml:mi>C</mml:mi><mml:mo>˜</mml:mo></mml:mover><mml:mn>4</mml:mn></mml:msub></mml:math>
International journal of mathematics and mathematical sciences