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 1-5 of 5 results.

A049407 Numbers m such that m^3 + m + 1 is prime.

Original entry on oeis.org

1, 2, 3, 5, 6, 8, 9, 12, 15, 17, 18, 21, 29, 30, 32, 39, 41, 42, 44, 48, 53, 54, 56, 60, 69, 71, 74, 77, 83, 87, 95, 102, 104, 108, 116, 117, 120, 126, 131, 135, 143, 144, 146, 152, 153, 155, 162, 168, 177, 179, 180, 186, 191, 207, 212, 219, 221, 225, 239, 240, 243
Offset: 1

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Comments

For s = 5, 8, 11, 14, 17, 20, ... (A016789(s) for s>=2), m_s = 1 + m + m^s is composite for m>1. Also for m=1, m_s = 3 is a prime for any s. Here we consider the case s=3.
If m == 1 (mod 3), m_s == 0 (mod 3) for any s and is not prime for m > 1. Thus for n > 1, a(n) !== 1 (mod 3) and this is true for any similar sequence based on another s value (A002384, A049408, A075723). - Jean-Christophe Hervé, Sep 20 2014
Corresponding primes are in A095692.

Examples

			3 is a term because 1 + 3 + 3^3 = 31 is a prime.
		

Crossrefs

Cf. A002384 (s=2), A049408 (s=4), A075723 (s=6).
Cf. A095692 (corresponding primes).

Programs

  • Magma
    [n: n in [0..300] | IsPrime(s) where s is 1+&+[n^i: i in [1..3 by 2]]]; // Vincenzo Librandi, Jun 27 2014
    
  • Maple
    A049407:=n->`if`(isprime(n^3+n+1), n, NULL): seq(A049407(n), n=1..300); # Wesley Ivan Hurt, Nov 14 2014
  • Mathematica
    Select[Range[500], PrimeQ[Total[#^Range[1, 3, 2]] + 1] &] (* Vincenzo Librandi, Jun 27 2014 *)
  • PARI
    is(n)=isprime(n^3+n+1) \\ Charles R Greathouse IV, Nov 20 2012
    
  • Python
    from sympy import isprime
    def ok(m): return isprime(m**3 + m + 1)
    print([m for m in range(244) if ok(m)]) # Michael S. Branicky, Feb 17 2022

A163421 Primes of the form ((p-1)/2)^3+((p+1)/2), p are prime numbers.

Original entry on oeis.org

3, 11, 31, 131, 223, 521, 739, 3391, 5851, 9283, 24419, 27031, 59359, 68963, 85229, 110641, 148931, 157519, 175673, 328579, 405299, 571871, 857471, 1561013, 1728121, 2248223, 2460511, 3112283, 3581731, 3724031, 4741801, 5735519
Offset: 1

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Comments

Subsequence of A095692.
((3-1)/2)^3+((3+1)/2)=1+2=3, ((5-1)/2)^3+((5+1)/2)=8+3=11, ((7-1)/2)^3+((7+1)/2)=27+4=31,..

Crossrefs

Programs

  • Mathematica
    f[n_]:=((p-1)/2)^3+((p+1)/2); lst={};Do[p=Prime[n];If[PrimeQ[f[p]],AppendTo[lst,f[p]]],{n,6!}];lst

Extensions

Comment from Charles R Greathouse IV, Aug 11 2009

A163422 Primes p such that A071568((p-1)/2) is also prime.

Original entry on oeis.org

3, 5, 7, 11, 13, 17, 19, 31, 37, 43, 59, 61, 79, 83, 89, 97, 107, 109, 113, 139, 149, 167, 191, 233, 241, 263, 271, 293, 307, 311, 337, 359, 373, 383, 439, 443, 479, 487, 491, 523, 557, 617, 641, 647, 659, 673, 683, 701, 733, 757, 811, 829, 853, 857, 859, 877
Offset: 1

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Comments

Primes p such that (p-1)^3/8+(p+1)/2 is also prime, i.e., in A095692.

Examples

			p=3 is in the sequence because (3-1)^3/8+(3+1)/2=3 is prime.
p=5 is in the sequence because (5-1)^3/8+(5+1)/2=11 is prime.
		

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(1000) | IsPrime((p^3-3*p^2+7*p+3) div 8)]; // Vincenzo Librandi, Apr 10 2013
  • Mathematica
    f[n_]:=((n-1)/2)^3+((n+1)/2); lst={}; Do[p=Prime[n]; If[PrimeQ[f[p]], AppendTo[lst, p]], {n,6!}]; lst
    Select[Prime[Range[180]], PrimeQ[(#-1)^3/8+(#+1)/2]&]  (* Harvey P. Dale, Jan 05 2011 *)

Extensions

Definition rewritten by R. J. Mathar, Aug 17 2009

A165946 Primes of the form p + (p-1)^3, where p is also prime.

Original entry on oeis.org

3, 11, 223, 1741, 5851, 27031, 74131, 216061, 1061311, 1259821, 2000503, 4251691, 5832181, 13824241, 21024853, 30371641, 37933393, 49028263, 54010531, 67917721, 84028111, 123506491, 162771883, 185193571, 191103553, 216000601, 229221541, 250047631, 264609931
Offset: 1

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Author

Claudio Meller, Oct 01 2009

Keywords

Comments

Generated by p = 2, 3, 7, 13, 19, 31, 43, 61, 103, 109, 127,... [R. J. Mathar, Oct 28 2009]

Crossrefs

Cf. A095692, A163421. [R. J. Mathar, Oct 28 2009]

Programs

  • Magma
    [a: p in PrimesInInterval(1, 1000) | IsPrime(a) where a is p + (p - 1)^3]; // Vincenzo Librandi, Oct 12 2012
  • Mathematica
    Select[Table[Prime[i] + (Prime[i] - 1)^3, {i, 300}], PrimeQ] (* Harvey P. Dale, Oct 07 2009 *)
    Select[Table[p + (p - 1)^3, {p, Prime[Range[300]]}], PrimeQ] (* Vincenzo Librandi, Oct 12 2012 *)

Extensions

5 more terms from R. J. Mathar, Oct 28 2009

A182332 Primes of the form n^3 + n - 1.

Original entry on oeis.org

29, 67, 349, 1009, 3389, 4111, 5849, 9281, 15649, 19709, 35969, 46691, 59357, 79549, 97381, 132701, 140659, 166429, 250109, 389089, 474629, 531521, 658589, 804449, 830677, 884831, 1000099, 1092829, 1157729, 1295137, 1405039, 1520989, 1601729, 1728119, 1906747
Offset: 1

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Author

Alex Ratushnyak, Apr 25 2012

Keywords

Comments

Infinite under Bunyakovsky's conjecture. - Charles R Greathouse IV, Apr 25 2012

Crossrefs

Programs

Showing 1-5 of 5 results.