>>12915400If he means {n+1 | n ? Z}, then this set is bijective to Z (hence equivalent in the sense of Cantor's theory of cardinals). You can define many bijections between then, but the "identity" itself does the job: define f:Z--->{n+1 | n ? Z} via f(m)=m. Clearly, m ? {n+1 | n ? Z}, because m-1 ? Z, so it is "well defined". f is *obviously* injective and surjective, hence bijective.
