We have shown by machine proof that F22 = 22 +1 is composite. In addition, we reenacted Young and Buell's 1988 resolution of F20 as composite, finding agreement with their final Selfridge-Hurwitz residues. We also resolved the character of all extant cofactors of Fn , n < 22, finding no new primes, and ruling out prime powers.

Abstract. We have shown by machine proof that F22 = 22 +1 is composite. In addition, we reenacted Young and Buell's 1988 resolution of F20 as composite, finding agreement with their final Selfridge-Hurwitz residues. We also resolved the character of all extant cofactors of Fn , n < 22, finding no new primes, and ruling out prime powers.