Order 20 Hexamagic Series Impossibility Theorem. There are no order 20 hexamagic series. Proof. S1 = 4010 ≡ 6 (mod 7) S2 = 1070670 ≡ 6 (mod 7) S3 = 321602000 ≡ 6 (mod 7) S4 = 103041066666 ≡ 6 (mod 7) S5 = 34389866666000 ≡ 6 (mod 7) S6 = 11805513142323810 ≡ 0 (mod 7) From the Modulo 7 Hexamagic Series Lemma, this hexamagic series must have 5 entries of 1 (mod 7) and 6 entries of 2...6 (mod 7). An order 20 hexamagic series must contain at least 35 entries.