= 0 mod p ͷ 0 ͔Β p − 1 ·Ͱͷղͷݸ ap Λٻ ΊΑɻ ࣮ݧ͢Δɻίʔυͪ͜Βɻ ap = 0 p = 3, 7, 11, 19, 23, 31, 43, . . . ap = 1 p = 2 ap = 2 p = 5, 13, 17, 29 37, 41, 53, . . . p Λ 4 Ͱׂͬͨ༨Γ p mod 4 ʹɻx2 + 1 = 0 ͱ 4 ͷؔɻ 1. ผࣜ D = b2 − 4ac = −4 Ͱ͋Δɻ 2. i4 = 1 Ͱ͋Δɻ ap − 1 ઌ΄Ͳͷ 1, 0, −1, 0, 1, 0, −1, 0, . . . ͱ͍͏ྻͱಉ͡ɻ 13/36