Quadratic Residues

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    px

    np

    np

    p

    p

    a

    p

    =

    1 x Z x2 a p1 x Z x2 a p0 a 0 p

    a

    p

    (a)p12 p

    p

    q

    p

    q

    =

    q

    p

    p q 3

    4

    p

    q

    =

    q

    p

    a b p a

    p = b

    p

    ab

    q

    =

    a

    q

    b

    q

    a+n a+ 2n a n Z gcd(a, n) = 1

    n n

    p

    = 1 p > n

    n n= 2kqk11 qk22 qkrr

    P > n n

    P

    = 1

    pn

    p

    =

    2

    p

    kq1

    p

    k1 q2p

    k2

    qr

    p

    kr=

    2

    p

    k

    n

    ki k

    P > n P 3 8 n

    P

    =

    2

    P

    k= (1)kP

    218 = 1.

    P > n

    8k+ 3

    8k+ 3

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    pi i

    8k+ 3 pn

    N=

    n

    i=1

    p2i + 2.

    gcd(N, pi) = 1i pi 1 i n 8k+ 3 p 3 8 p | N p | N p 1 5 7 8

    ni=1p

    2i + 2 0 p p | N

    =ni=1

    p2i 2 p =n

    i=1p2i

    p

    = 1 =

    2p

    =2

    p

    =

    1p

    2

    p

    = (1)p12 (1)p

    218 = 1

    p 1 8 p 8k+ 3

    N

    8k+ 1

    8k + 1 8k + 1 N 3 8

    8k + 1 8k + 3

    ki k1

    P > n P 1 8 P t q1 t q1 P 1 qi 2 i r

    n

    p

    =

    2

    p

    k q1

    p

    k1 q2p

    k2

    qr

    p

    kr=

    q1

    p

    k1

    =P

    q1k1

    = t

    q1k1

    = (1)k1

    = 1. P t

    n

    t+ q1k > q1 t q1 8 q1 q2 qr P

    P > n nP

    = 1

    n n

    p

    = 1 p > n

    n= 2k

    qk11 q

    k22 q

    krr

    P > n n

    P

    = 1

    p

    n

    p

    =

    2

    p

    kq1

    p

    k1 q2p

    k2

    qr

    p

    kr=

    2

    p

    k

    n

    ki k

    P > n P 1 8

    nP = 2

    Pk

    = (

    1)k

    P218 = 1.

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    P > n

    8k+ 1

    8k+ 1

    pi

    i

    8k+ 1 pn

    M =

    ni=1

    pi ; N=M4 + 1

    gcd(N, pi) = 1i N p | N N=

    M22

    + 12 p 4k + 1 8k + 5 8k+ 1 pi| N p 8k+ 5

    M4 + 1 M4 + 2M2 + 1 2M2 0 p= M

    2 12 2M2 0 p

    = M2 12 2M2

    p

    M2 12

    p

    = 1 =

    2M2p

    =

    1p

    2

    p

    M2

    p

    = (1)p12 (1)p

    218

    p

    8k+ 5

    1 = (1) (1) = 1 p 8k+ 1 p1, p2, , pn

    x4

    1 p p 1 8

    ki k1

    P > n P 1 8 P s q1 s q1 P 1 qi 2 i r

    n

    p

    =

    2

    p

    k q1

    p

    k1 q2p

    k2

    qr

    p

    kr=

    q1

    p

    k1

    =

    P

    q1

    k1=

    s

    q1

    k1= (1)k1 = 1.

    P

    s+ q1k > q1 s q1 8 q1 q2 qr P

    px

    np

    n= m2

    m Z px

    n

    p

    =px

    1 d(n) =(x) d(n)

    d(n)

    n

    (x)

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    n px

    n

    p

    n

    px

    n

    p

    =o ((x))

    x

    px

    n

    p

    =px

    p

    n

    ; = {1, 1}

    p x a + kn a n

    px

    p

    n =

    apamodnx

    a

    na,n(x)

    a,n(x) a+ n a+ 2n a+ 3n x

    a,n(x) 1(n)

    (x)

    px

    p

    n

    a

    pamodnx

    a

    n

    1(n)

    (x).

    px

    pn

    a

    pamodnx

    an

    (x)(n)

    < a

    pamodnx

    an

    1(n)

    (x).

    px

    n

    p

    apamodnx

    a

    n

    (x)(n)

    < a

    pamodnx

    1.(x)

    (n)

    (n) a

    pxn

    p apamodnx

    a

    n(x)

    (n) < (n)(x)

    (n) =(x)

    =px

    n

    p

    N n a2 p = n

    a

    2

    +kp

    p

    N

    x

    2

    , y

    2

    N x < y

    y2 x2 = (y+x) (y x) = p.1 1 p y x = 1 y+ x = p x y x, y > N a2 +kp

    12

    px

    n

    p

    =o ((x)) = PR(n) =PNR(n) = 1

    2.

    px

    np

    =o ((x)) 12

    12

    px

    np

    = o ((x))

    PR(n) = 1

    2=PNR(n) =

    px

    n

    p

    =o ((x))

    n n 1 4. px

    n

    p

    = 0

    x

    px

    n

    p

    =px

    pn

    .

    n

    12

    limxpx

    pn

    = 0

    +1

    1

    n 3 4 px

    n

    p

    =

    px

    p1mod4

    pn

    px

    p3mod4

    pn

    .

    n

    px

    pn =

    pxp1mod4

    pn+

    pxp3mod4

    pn = 0

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    =px

    p3mod4

    pn

    =

    px

    p1mod4

    pn

    n 3 4 px

    n

    p

    = 2

    px

    p1mod4

    pn

    =px

    n

    p

    = 2

    px

    p3mod4

    pn

    .

    px

    np

    0

    x n

    n

    p

    n

    p

    n

    p

    = 1

    n

    P n

    P

    = 1

    limx

    px

    n

    p

    = lim

    x

    pP

    n

    p

    +

    P P

    limx

    pP

    n

    p

    +

    P

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    Q

    a1,

    a2, , al

    Q

    http://en.wikipedia.org/wiki/Quadratic_reciprocityhttp://en.wikipedia.org/wiki/Dirichlet's_theorem_on_arithmetic_progressionshttp://en.wikipedia.org/wiki/Prime_number_theorem