User blog comment:Alemagno12/Rayo and FOST/@comment-27173506-20160331154639/@comment-1605058-20160401150125

If I'm not mistaken, it should be "(¬∃n(n∈a0))" and "(...∧(an∈an+1∧((¬∃n(n∈an∧(¬n∈an+1)))∧(¬∃n((n∈an+1∧((¬n=an)∧(¬n∈an))))))))"