cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-6 of 6 results.

A331945 Factors k > 0 such that the polynomial k*x^2 + 1 produces a record of its Hardy-Littlewood constant.

Original entry on oeis.org

1, 2, 3, 4, 12, 18, 28, 58, 190, 462, 708, 5460, 10602, 39292, 141100, 249582, 288502
Offset: 1

Views

Author

Hugo Pfoertner, Feb 10 2020

Keywords

Comments

a(18) > 510000.
See A331940 for more information on the Hardy-Littlewood constant. The polynomials described by this sequence have an increasing rate of generating primes.
The following table provides the record values of the Hardy-Littlewood constant C, together with the number of primes np generated by the polynomial P(x) = a(n)*x^2 + 1 for 1 <= x <= r = 10^8 and the actual ratio np*(P(r)/r)/Integral_{x=2..P(r)} 1/log(x) dx.
a(n) C np C from ratio
1 1.37281 3954181 1.41606 (C = A199401)
2 1.42613 4027074 1.47010
3 1.68110 4696044 1.73337
4 2.74563 7605407 2.82915
12 3.36220 9037790 3.46135
.. ....... ....... .......
249582 7.90518 16760196 8.08633
288502 8.21709 17367067 8.40431

References

  • Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209.

Crossrefs

A331947 Factors k > 1 such that the polynomial k*x^2 - 1 produces a record of its Hardy-Littlewood constant.

Original entry on oeis.org

2, 12, 20, 68, 90, 98, 132, 252, 318, 362, 398, 1722, 259668, 315180, 452042
Offset: 1

Views

Author

Hugo Pfoertner, Feb 10 2020

Keywords

Comments

a(16) > 710000.
See A331940 for more information on the Hardy-Littlewood constant. The polynomials described by this sequence have an increasing rate of generating primes.
The following table provides the record values of the Hardy-Littlewood constant C, together with the number of primes np generated by the polynomial P(x) = a(n)*x^2 - 1 for 2 <= x <= r = 10^8 and the actual ratio np*(P(r)/r)/Integral_{x=2..P(r)} 1/log(x) dx.
a(n) C np C from ratio
2 3.70011 10448345 3.81422
12 4.15027 11154934 4.27219
20 4.43326 11753085 4.56136
68 5.01601 12883801 5.15797
.. ....... ........ .......
315180 7.82318 16502584 8.00057
452042 7.85323 16434699 8.02696

References

  • Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209.

Crossrefs

A003420 Values of m in the discriminant D = -4*m leading to a new maximum of the L-function of the Dirichlet series L(1) = Sum_{k=1..oo} Kronecker(D,k)/k.

Original entry on oeis.org

1, 2, 5, 11, 14, 26, 41, 89, 101, 194, 314, 341, 689, 1091, 1154, 1889, 2141, 3449, 3506, 5561, 6254, 8126, 8774, 10709, 13166, 15461, 23201, 24569, 30014, 81149, 81626, 162686, 243374, 644474, 839354, 879941
Offset: 1

Views

Author

Keywords

Comments

In Shanks's Table 5 "Hichamps, -4N = Discriminant", N = 1 is omitted, and N = 23201 is missing. Shanks describes the table as being tentative after N = 24569. In Buell's Table 10 "Successive maxima of L(1) for even discriminants", the values N = 11 and N = 1091 are missing in the D/4 column. The further terms 644474, 839354, 879941, provided there require an independent check. - Hugo Pfoertner, Feb 02 2020

Examples

			a(1) = 1: L(1) for D=-4*1 ~= 0.785398... = Pi/4.
a(2) = 2: L(1) for D=-4*2 ~= 1.11072073... = Pi/(2*sqrt(2)), a(2) > a(1);
L(1) for D=-4*3 ~= 0.90689..., L(1) for D=-4*4 ~= 0.785398..., both < a(2);
a(3) = 5: L(1) for D=-4*5 = 1.40496..., a(3) > a(2).
		

References

  • D. Shanks, Systematic examination of Littlewood's bounds on L(1,chi), pp. 267-283 of Analytic Number Theory, ed. H. G. Diamond, Proc. Sympos. Pure Math., 24 (1973). Amer. Math. Soc.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A003521.
Cf. A331949, which has almost identical terms.

Extensions

New title, a(1) prepended, missing term 23201 and a(29)-a(33) from Hugo Pfoertner, Feb 02 2020
3 further terms < 10^6 added by Hugo Pfoertner, Aug 27 2022

A332707 Factors k > 2 such that the polynomial x^2 + k*x + 1 produces a new minimum of its Hardy-Littlewood constant.

Original entry on oeis.org

3, 4, 8, 20, 40, 230, 260, 680, 1910, 2120, 6670, 9710, 10310, 23500, 25220, 37990, 71800
Offset: 1

Views

Author

Hugo Pfoertner, Feb 20 2020

Keywords

Comments

a(18) > 100000.
See A331940 for more information on the Hardy-Littlewood constant. The polynomials described by this sequence are increasingly avoiding primes.
The following table provides the minimum values of the Hardy-Littlewood constant C, together with the number of primes np generated by the polynomial P(x) = x^2 + a(n)*x + 1 for 1 <= x <= r = 10^8 and the actual ratio np*(P(r)/r)/Integral_{x=2..P(r)} 1/log(x) dx.
a(n) C np C from ratio
3 3.54661 10220078 3.65998
4 1.38342 3982973 1.42637
8 0.91172 2627239 0.94086
20 0.76532 2204290 0.78939
..... ....... ....... .......
25220 0.39947 1151122 0.41224
37990 0.39945 1151126 0.41224

References

  • Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209.

Crossrefs

A332708 Factors k >= 0 such that the polynomial x^2 + k*x + 1 produces a record of its Hardy-Littlewood constant.

Original entry on oeis.org

1, 3, 21, 231, 879, 1011, 1089, 1659, 2751
Offset: 1

Views

Author

Hugo Pfoertner, Feb 20 2020

Keywords

Comments

a(10) > 80000.
See A331940 for more information on the Hardy-Littlewood constant. The polynomials described by this sequence have an increasing rate of generating primes.
The following table provides the record values of the Hardy-Littlewood constant C, together with the number of primes np generated by the polynomial P(x) = x^2 + a(n)*x + 1 for 1 <= x <= r = 10^8 and the actual ratio np*(P(r)/r)/Integral_{x=2..P(r)} 1/log(x) dx.
a(n) C np C from ratio
1 2.24147 6456835 2.31230
3 3.54661 10220078 3.65998
21 5.58679 16096923 5.76458
231 5.74156 16543757 5.92460
879 5.83722 16813676 6.02126
1011 5.92725 17073610 6.11435
1089 6.03701 17392675 6.22861
1659 6.04359 17413761 6.23617
2751 7.46622 21508374 7.70252

References

  • Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209.

Crossrefs

A342569 Noncube addends k > 0 such that x^3 + k produces a new minimum of its Hardy-Littlewood constant.

Original entry on oeis.org

2, 5, 6, 13, 15, 20, 34, 83, 174, 246, 911, 1065, 1084, 1455, 1490, 1546, 3674, 8644, 9556, 15287, 15378, 15826, 25670
Offset: 1

Views

Author

Hugo Pfoertner, May 03 2021

Keywords

Comments

a(24) > 42500.
For more information and references see A331950.

Examples

			   n  a(n)   Hardy-Littlewood         np / (expected number of primes)
             constant (rounded)       obtained from Li((10^9)^3+a(n))
                        np (x<=10^9)  (similar to table in A331946)
   1     2   1.298539558  22009948    1.34597
   2     5   1.142678324  19372839    1.18470
   3     6   0.822719287  13944026    0.85272
   4    13   0.814418714  13802244    0.84405
   5    15   0.784789179  13305075    0.81364
  ...
  20 15287   0.422422003   7162493    0.43801
  21 15378   0.419380705   7108723    0.43472
  22 15826   0.416982640   7068923    0.43228
  23 25670   0.388993112   6597073    0.40343
		

Crossrefs

Cf. A331946, A331949 (similar for x^2+k), A331950, A342547.
Showing 1-6 of 6 results.