A001480 -id:A001480 - cp's OEIS frontend

A271228 P-defects p - N(p) of the elliptic curve y^2 = x^3 + 17 for primes p, where N(p) is the number of solutions modulo prime p.

0, 0, 0, -5, 0, -7, 0, -7, 0, 0, -11, -11, 0, -13, 0, 0, 0, 13, 5, 0, 10, 4, 0, 0, -5, 0, -7, 0, -2, 0, -19, 0, 0, 7, 0, -19, -25, -8, 0, 0, 0, 7, 0, -23, 0, 28, 13, -28, 0, -22

Offset: 1

Wolfdieter Lang, Apr 21 2016

See A271227 for details and the conjecture for a(n) if prime(n) == 1 (mod 3).

a(n) is negative for the 1 (mod 3) primes 7, 13, 19, 31, 37, 43, 97, 103, 109, 127, 151, 157, 163, 193, 223, 229, 241, 271, 277, 307, 313, 331, ... and positive for the primes 61, 67, 73, 79, 139, 181, 199, 211, 283, 337, 349, ... See A271227 for a comment on the conjectured three types I, II, and III of 1 (mod 3) primes. All three types appear for primes with negative as well as positive a(n) values.

			n = 4, prime(4) = 7, A271227(4) = 12 (see the example in A271227 for the solutions), a(4) = 7 - 12 = -5. Prime 7 is of type II.
n = 25, prime(25) = 97, A271227(25) = 102, a(25) = -5. Prime 97 is of type III.
n = 29, prime(29) = 109, A271227(29) = 111, a(29) = -2. Prime 109 is of type I.
n = 18, prime(18) = 61, A271227(18) = 48, a(18) = +13. Prime 61 is of type II.
n = 19, prime(19) = 67, A271227(19) = 62, a(19) = +5. Prime 67 is of type III.
n = 21, prime(21) = 73, A271227(21) = 63, a(21) = +10. Prime 73 is of type I.

J. H. Silverman, A Friendly Introduction to Number Theory, 3rd ed., Pearson Education, Inc, 2006, Table 45.5, Theorem 45.2, p. 400, Exercise 45.3, p. 404, p. 408 (4th ed., Pearson 2014, Table 5, Theorem 2, p. 366, Exercise 3, p. 370, p. 376)

Seiichi Manyama, Table of n, a(n) for n = 1..10000

Cf. A271227.

a(n) = prime(n) - A271227(n), where  A271227(n) is the number of solutions of the congruence y^2 = x^3 + 17 (mod prime(n)).
a(n) = 0 precisely for prime(n) == 0, or 2 (mod 3). See the Silverman reference, pp. 400 - 402 for the proof. (The case 0 (mod 3) is trivial.)
Conjecture [WL]: For prime(n) = A002476(m) (a prime  == 1 (mod 3)) one has  a(n) = + or - sqrt(4*prime(n)) - 3*q(m)^2), with three alternative cases for q(m)^2, namely (2*B(m))^2, (A(m) - B(m))^2 and (A(m) + B(m))^2, where A(m) = A001479(m+1) and B(m) = A001480(m+1), m >= 1.

A272204 A bisection of the primes congruent to 1 modulo 3 (A002476). This is the part depending on the corresponding A001479 entry being congruent to 1 or 2 modulo 6.

Original entry on oeis.org

7, 13, 31, 61, 67, 79, 97, 109, 139, 151, 157, 181, 193, 199, 211, 223, 241, 271, 277, 307, 349, 367, 373, 409, 433, 439, 547, 571, 601, 643, 661, 673, 733, 739, 751, 757, 769, 823, 907, 919, 937

Offset: 1

Wolfdieter Lang, May 05 2016

The other part of this bisection appears in A272205.
Each prime == 1 (mod 3) has a unique representation A002476(m) = A(m)^2 + 3*B(m)^2 with positive A(m) = A001479(m+1) and B(m) = A001480(m+1), m >= 1. The present sequence gives all such primes corresponding to A(m) == 1, 2 (mod 6). The ones corresponding to A(m) not == 1, 2 (mod 6) (the complement), that is == 4, 5 (mod 6), are given in A272205.
The corresponding A001479 entries are 2, 1, 2, 7, 8, 2, 7, 1, 8, 2, 7, 13, 1, 14, 8, 14, 7, 14, 13, 8, 7, 2, 19, 19, 1, 14, 20, 8, 13, 20, 19, 25, 25, 8, 26, 13, 1, 26, 20, 26, 13, ...
This bisection of the 1 (mod 3) primes A002476 is needed to determine the sign in the formula for the coefficients of the q-expansion (q = exp(2*Pi*i*z), Im(z) > 0) of the modular weight 2 cusp form
  eta^{12}(12*z) / (eta^4(6*z)*eta^4(24*z)) |A187076%20which%20gives%20the%20coefficients%20of%20the%20q-expansion%20of%20F(q)%20=%20Eta(q%5E%7B1/6%7D)%20/%20q%5E%7B1/6%7D%20=%20Product">{z=z(q)} =: Eta(q) with Dedekind's eta function. See A187076 which gives the coefficients of the q-expansion of F(q) = Eta(q^{1/6}) / q^{1/6} = Product{m>=0} (1 - q^(2*m))^{12} / ((1 - q^m)*(1 - q^(4*m)))^4. The q-expansion coefficients (called b(n)) of the modular cusp form are given there using multiplicativity. Note that there x can also be negative, whereas here A is positive.

Cf. A001479, A001480, A002476, A047239, A187076, A272203, A272205 (complement relative to A002476).

This sequence collects the 1 (mod 3) primes p(m) = A002476(m) = A(m)^2 + 3*B(m)^2 with positive A(m) == 1, 2 (mod 6), for m >= 1. A(m) = A001479(m+1).

cp's OEIS Frontend

A271228 P-defects p - N(p) of the elliptic curve y^2 = x^3 + 17 for primes p, where N(p) is the number of solutions modulo prime p.

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