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.

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A242119 Primes modulo 18.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 17, 1, 5, 11, 13, 1, 5, 7, 11, 17, 5, 7, 13, 17, 1, 7, 11, 17, 7, 11, 13, 17, 1, 5, 1, 5, 11, 13, 5, 7, 13, 1, 5, 11, 17, 1, 11, 13, 17, 1, 13, 7, 11, 13, 17, 5, 7, 17, 5, 11, 17, 1, 7, 11, 13, 5, 1, 5, 7, 11, 7, 13, 5, 7, 11, 17, 7, 13, 1, 5
Offset: 1

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Author

Vincenzo Librandi, May 05 2014

Keywords

Crossrefs

Cf. sequences of the type Primes mod k: A039701 (k=3), A039702 (k=4), A039703 (k=5), A039704 (k=6), A039705 (k=7), A039706 (k=8), A038194 (k=9), A007652 (k=10), A039709 (k=11), A039710 (k=12), A039711 (k=13), A039712 (k=14), A039713 (k=15), A039714 (k=16), A039715 (k=17), this sequence (k=18), A033633 (k=19), A242120(k=20), A242121 (k=21), A242122 (k=22), A229786 (k=23), A229787 (k=24), A242123 (k=25), A242124 (k=26), A242125 (k=27), A242126 (k=28), A242127 (k=29), A095959 (k=30), A110923 (k=100).

Programs

  • Magma
    [p mod(18): p in PrimesUpTo(500)];
    
  • Mathematica
    Mod[Prime[Range[100]], 18]
  • Sage
    [mod(p, 18) for p in primes(500)] # Bruno Berselli, May 05 2014

Formula

Sum_{i=1..n} a(i) ~ 9n. The derivation is the same as in the formula in A039715. - Jerzy R Borysowicz, Apr 27 2022

A039704 a(n) = n-th prime modulo 6.

Original entry on oeis.org

2, 3, 5, 1, 5, 1, 5, 1, 5, 5, 1, 1, 5, 1, 5, 5, 5, 1, 1, 5, 1, 1, 5, 5, 1, 5, 1, 5, 1, 5, 1, 5, 5, 1, 5, 1, 1, 1, 5, 5, 5, 1, 5, 1, 5, 1, 1, 1, 5, 1, 5, 5, 1, 5, 5, 5, 5, 1, 1, 5, 1, 5, 1, 5, 1, 5, 1, 1, 5, 1, 5, 5, 1, 1, 1, 5, 5, 1, 5, 1, 5, 1, 5, 1, 1, 5, 5, 1, 5, 1, 5, 5, 1, 5, 1, 5, 5, 5, 1, 1, 1, 5, 5, 5, 1
Offset: 1

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Programs

Formula

Sum_k={1..n} a(k) ~ 3*n. - Amiram Eldar, Dec 11 2024

A039705 a(n) = n-th prime modulo 7.

Original entry on oeis.org

2, 3, 5, 0, 4, 6, 3, 5, 2, 1, 3, 2, 6, 1, 5, 4, 3, 5, 4, 1, 3, 2, 6, 5, 6, 3, 5, 2, 4, 1, 1, 5, 4, 6, 2, 4, 3, 2, 6, 5, 4, 6, 2, 4, 1, 3, 1, 6, 3, 5, 2, 1, 3, 6, 5, 4, 3, 5, 4, 1, 3, 6, 6, 3, 5, 2, 2, 1, 4, 6, 3, 2, 3, 2, 1, 5, 4, 5, 2, 3, 6, 1, 4, 6, 5, 2, 1, 2, 6, 1, 5, 3, 4, 1, 2, 6, 5, 3, 5, 2, 1, 4, 3, 2, 4
Offset: 1

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Keywords

Comments

a(A049084(A045370(n-1))) is even; a(A049084(A045415(n-1))) is odd. - Reinhard Zumkeller, Feb 25 2008

Crossrefs

Programs

Formula

Sum_k={1..n} a(k) ~ (7/2)*n. - Amiram Eldar, Dec 11 2024

A134323 a(n) = Legendre(-3, prime(n)).

Original entry on oeis.org

-1, 0, -1, 1, -1, 1, -1, 1, -1, -1, 1, 1, -1, 1, -1, -1, -1, 1, 1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, -1, 1, -1, -1, 1, -1, 1, 1, 1, -1, -1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, -1, -1, 1, -1, -1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, 1, -1, -1, 1, -1, 1, -1, 1, -1, 1, 1, -1, -1, 1, -1, 1, -1, -1, 1, -1, 1, -1, -1, -1, 1, 1, 1, -1
Offset: 1

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Author

Reinhard Zumkeller, Oct 21 2007

Keywords

Comments

Value of lowest trit of prime(n) in balanced ternary representation (A059095) (original definition).
For p = prime(n) != 3, a(n) = +1 if p is of the form 3*k + 1, and -1 if the p is of the form 3*k - 1. - Joerg Arndt, Sep 16 2014

Examples

			For n=20, prime(20) = 71, and we verify that -3 is not a quadratic residue modulo 71, hence a(20) = -1. Also, we see that the balanced ternary representation row A059095(71) = {1, 0, -1, 0, -1} which ends in -1.
For n=21, prime(21) = 73, and we see that x^2 = -3 mod 73 has solutions like x = 17, 56, hence a(21) = 1. Also, the balanced ternary representation row A059095(73) = {1, 0 -1, 0, 1} which ends in 1.
		

Crossrefs

Cf. A000040, A039701, A049084, A112632 (partial sums), A059095 (balanced ternary)
Cf. A091177 (indices of -1's), A091178 (indices of +1's), A003627, A002476.
Other moduli: A070750, A257834.
Cf. A102283.

Programs

Formula

-1 if the n-th prime is 2 or == 5 mod 6, +1 if the n-th prime is == 1 mod 6, and 0 if it is 3.
a(n) = (1 - 0^A039701(n)) * (-1)^(A039701(n)+1).
a(n) != 0 for n != 2;
a(A049084(A003627(n))) = -1; a(A049084(A002476(n))) = +1.
a(n) = A102283(prime(n)). - Ridouane Oudra, Jan 09 2025

Extensions

Wording of definition changed by N. J. A. Sloane, Jun 21 2015
Name simplified by Alonso del Arte, Aug 02 2017

A103566 Sum of the primes > 5 modulo 3.

Original entry on oeis.org

1, 3, 4, 6, 7, 9, 11, 12, 13, 15, 16, 18, 20, 22, 23, 24, 26, 27, 28, 30, 32, 33, 35, 36, 38, 39, 41, 42, 44, 46, 47, 49, 50, 51, 52, 54, 56, 58, 59, 61, 62, 64, 65, 66, 67, 69, 70, 72, 74, 75, 77, 79, 81, 83, 84, 85, 87, 88, 90, 91, 93, 94, 96, 97, 98, 100, 101, 103, 105, 106
Offset: 1

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Author

Roger L. Bagula, Mar 23 2005

Keywords

Crossrefs

Programs

  • Mathematica
    a = Table[Sum[Mod[Prime[i + 3], 3], {i, 1, n}], {n, 1, 200}]
    Accumulate[Mod[Prime[Range[4,80]],3]] (* Harvey P. Dale, Aug 04 2013 *)

Formula

a(n+1)-a(n) = A039701(n+4) (first differences).
a(n) = A120326(n+3) - 4. - Jason Yuen, Sep 01 2024

A039710 a(n) = n-th prime modulo 12.

Original entry on oeis.org

2, 3, 5, 7, 11, 1, 5, 7, 11, 5, 7, 1, 5, 7, 11, 5, 11, 1, 7, 11, 1, 7, 11, 5, 1, 5, 7, 11, 1, 5, 7, 11, 5, 7, 5, 7, 1, 7, 11, 5, 11, 1, 11, 1, 5, 7, 7, 7, 11, 1, 5, 11, 1, 11, 5, 11, 5, 7, 1, 5, 7, 5, 7, 11, 1, 5, 7, 1, 11, 1, 5, 11, 7, 1, 7, 11, 5, 1, 5, 1, 11
Offset: 1

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Formula

Sum_k={1..n} a(k) ~ 6*n. - Amiram Eldar, Dec 11 2024

A039711 a(n) = n-th prime modulo 13.

Original entry on oeis.org

2, 3, 5, 7, 11, 0, 4, 6, 10, 3, 5, 11, 2, 4, 8, 1, 7, 9, 2, 6, 8, 1, 5, 11, 6, 10, 12, 3, 5, 9, 10, 1, 7, 9, 6, 8, 1, 7, 11, 4, 10, 12, 9, 11, 2, 4, 3, 2, 6, 8, 12, 5, 7, 4, 10, 3, 9, 11, 4, 8, 10, 7, 8, 12, 1, 5, 6, 12, 9, 11, 2, 8, 3, 9, 2, 6, 12, 7, 11, 6
Offset: 1

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Formula

Sum_k={1..n} a(k) ~ (13/2)*n. - Amiram Eldar, Dec 11 2024

A039712 a(n) = n-th prime modulo 14.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 3, 5, 9, 1, 3, 9, 13, 1, 5, 11, 3, 5, 11, 1, 3, 9, 13, 5, 13, 3, 5, 9, 11, 1, 1, 5, 11, 13, 9, 11, 3, 9, 13, 5, 11, 13, 9, 11, 1, 3, 1, 13, 3, 5, 9, 1, 3, 13, 5, 11, 3, 5, 11, 1, 3, 13, 13, 3, 5, 9, 9, 1, 11, 13, 3, 9, 3, 9, 1, 5, 11, 5, 9
Offset: 1

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Formula

Sum_k={1..n} a(k) ~ 7*n. - Amiram Eldar, Dec 12 2024

A039713 a(n) = n-th prime modulo 15.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 2, 4, 8, 14, 1, 7, 11, 13, 2, 8, 14, 1, 7, 11, 13, 4, 8, 14, 7, 11, 13, 2, 4, 8, 7, 11, 2, 4, 14, 1, 7, 13, 2, 8, 14, 1, 11, 13, 2, 4, 1, 13, 2, 4, 8, 14, 1, 11, 2, 8, 14, 1, 7, 11, 13, 8, 7, 11, 13, 2, 1, 7, 2, 4, 8, 14, 7, 13, 4, 8, 14, 7
Offset: 1

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Programs

Formula

Sum_k={1..n} a(k) ~ (15/2)*n. - Amiram Eldar, Dec 12 2024

A039714 a(n) = n-th prime modulo 16.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 1, 3, 7, 13, 15, 5, 9, 11, 15, 5, 11, 13, 3, 7, 9, 15, 3, 9, 1, 5, 7, 11, 13, 1, 15, 3, 9, 11, 5, 7, 13, 3, 7, 13, 3, 5, 15, 1, 5, 7, 3, 15, 3, 5, 9, 15, 1, 11, 1, 7, 13, 15, 5, 9, 11, 5, 3, 7, 9, 13, 11, 1, 11, 13, 1, 7, 15, 5, 11, 15, 5
Offset: 1

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Author

Keywords

Crossrefs

Programs

Formula

Sum_k={1..n} a(k) ~ 8*n. - Amiram Eldar, Dec 12 2024
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