The City of Tulsa charter says this (emphasis added) in Article VII, Section 2.1:

If the officer sought to be recalled was elected from an election district, a preliminary petition for recall of the elected officer must contain the signatures of qualified electors residing in the election district involved equal in number to ten percent (10%) of all those voting in that election district for the affected office in the preceding general election.

And in Section 3:

If the officer sought to be recalled was elected from an election district, supporting petitions to be sufficient must contain the signatures of qualified electors residing in the election district involved equal in number to twenty-five percent (25%) of all those voting in that election district for the affected office in the preceding general election.

When was the preceding general election? March 9, 2004.

How many people voted in the District 7 council race in that general election? 0; Randy Sullivan had primary opposition but was unopposed in the general.

How many people voted in the District 8 council race in that general election? 0; Bill Christiansen had primary opposition but was unopposed in the general.

What is 10% of 0? 0.

What is 25% of 0? 0.

How many signatures would it take to trigger a recall election against Randy Sullivan or Bill Christiansen? One each.