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. p = 19 m −1 = 17 m +1 = p
. p = 15 m +1 = 17 m −1 = p
. p = 19
p ()
6 p 2 +11
7( ) 5( ) 3( ) 2()
:( )
. 4 22 +11 = 15 = 3× 5
52 +11 = 36 = 22 × 32 . 6 32 +11 = 20 = 22 × 5
72 +11 = 60 = 22 ×3× 5 . 9
.( ) . 12
. 18 4 q p [AMC10A 2000] ( )
231 ( )
pq − ( p + q )
119 ( ) 60 ( ) 21 ( )
k = pq − (p + q ) :( )
k +1 = pq − p − q +1 = ( p −1) (q −1)
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