  This paper calculates the number of full exceptional collections modulo an
action of a group as the set generated by spherical twists for an abelian
category of coherent sheaves on an orbifold projective line with a zero
orbifold Euler characteristic. This is done by a recursive formula naturally
generalizing the one for the Dynkin case by Deligne whose categorical
interpretation is due to Obaid-Nauman-Shammakh-Fakieh-Ringel and an abelian
category of coherent sheaves on an orbifold projective line with a positive
orbifold Euler characteristic is due to Otani-Shiraishi-Takahashi.
