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.

A129738 List of primitive prime divisors of the Jacobsthal numbers A001045 in their order of occurrence.

Original entry on oeis.org

3, 5, 11, 7, 43, 17, 19, 31, 683, 13, 2731, 127, 331, 257, 43691, 73, 174763, 41, 5419, 23, 89, 2796203, 241, 251, 4051, 8191, 87211, 29, 113, 59, 3033169, 151, 715827883, 65537, 67, 20857, 131071, 281, 86171, 37, 109, 1777, 25781083, 524287, 22366891, 61681, 83
Offset: 1

Views

Author

N. J. A. Sloane, May 13 2007

Keywords

Comments

Read A001045 term-by-term, factorize each term, write down any primes not seen before.

Crossrefs

Programs

  • Maple
    concat := (a,h)->[op(a),op(sort(convert(h,list)))]:
    PPDinOrder := proc(S) local A,H,T,s;
    T := {0,1}; A := [];
    for s in S do
      H := numtheory[factorset](s) minus T:
      if H <> {} then
        A := concat(A,H);
        T := T union H
      fi
    od;
    A end:
    A129738 := PPDinOrder(A001045);
    # Peter Luschny, Jan 04 2011
  • Mathematica
    DeleteDuplicates[Flatten[FactorInteger[#][[All,1]]&/@LinearRecurrence[ {1,2},{3,5},50]]](* Harvey P. Dale, Apr 14 2020 *)

A129736 Primes of the form 4^k - 3^k.

Original entry on oeis.org

7, 37, 14197, 17050729021, 332306984815842876487217260305275077
Offset: 1

Views

Author

N. J. A. Sloane, May 13 2007

Keywords

Crossrefs

Programs

  • GAP
    Filtered(List([1..100], n -> 4^n-3^n), IsPrime); # Muniru A Asiru, Feb 09 2018
    
  • Magma
    [a: n in [0..300] | IsPrime(a) where a is 4^n-3^n]; // Vincenzo Librandi, Nov 23 2010
    
  • Maple
    select(isprime, [seq(4^n - 3^n, n=0..100)]); # Muniru A Asiru, Feb 09 2018
  • Mathematica
    fQ[n_] := If[PrimeQ[4^n - 3^n], 4^n - 3^n, Nothing]; Array[fQ, 300] (* Robert G. Wilson v, Feb 12 2018 *)
  • PARI
    lista(nn) = for(k=1, nn, if(isprime(p=4^k-3^k), print1(p", "))) \\ Altug Alkan, Mar 03 2018

Formula

a(n) = A005061(A059801(n)). - Michel Marcus, Feb 12 2018

A129735 List of primitive prime divisors of the numbers (4^n-1)/3 (A002450) in their order of occurrence.

Original entry on oeis.org

5, 3, 7, 17, 11, 31, 13, 43, 127, 257, 19, 73, 41, 23, 89, 683, 241, 2731, 8191, 29, 113, 151, 331, 65537, 43691, 131071, 37, 109, 174763, 524287, 61681, 337, 5419, 397, 2113, 47, 178481, 2796203, 97, 673, 251, 601, 1801, 4051, 53, 157, 1613, 87211, 262657, 15790321, 59, 233, 1103, 2089, 3033169, 61, 1321, 715827883, 2147483647
Offset: 1

Views

Author

N. J. A. Sloane, May 13 2007

Keywords

Comments

Read A002450 term-by-term, factorize each term, write down any primes not seen before in increasing order for each term.

Examples

			The primes grouped according to successive terms of A002450, courtesy of _James R. Buddenhagen_:
[5], [3, 7], [17], [11, 31], [13], [43, 127], [257], [19, 73], [41], [23, 89, 683], [241], [2731, 8191], [29, 113], [151, 331], [65537], [43691, 131071], [37, 109], [174763, 524287], [61681], [337, 5419], [397, 2113], [47, 178481, 2796203], [97, 673], [251, 601, 1801, 4051], [53, 157, 1613], [87211, 262657], [15790321], [59, 233, 1103, 2089, 3033169], [61, 1321], [715827883, 2147483647], ...
		

Crossrefs

Extensions

Order of terms corrected by James R. Buddenhagen, Jul 23 2015

A129737 List of primitive prime divisors of the numbers 4^n-3^n (A005061) in their order of occurrence.

Original entry on oeis.org

7, 37, 5, 11, 71, 13, 14197, 337, 6553, 181, 23, 174659, 193, 131, 500111, 379, 61, 601, 17, 4241, 17050729021, 19, 163, 10814953, 25309, 8861, 8352709, 727, 859, 47, 44483, 17389, 1933, 51361, 1440528320401, 313, 31357, 36174709, 2053, 29, 376853, 59, 349
Offset: 1

Views

Author

N. J. A. Sloane, May 13 2007

Keywords

Comments

Read A005061 term-by-term, factorize each term, write down any primes not seen before.

Crossrefs

A129734 List of primitive prime divisors of the numbers 3^n-2^n (A001047) in their order of occurrence.

Original entry on oeis.org

5, 19, 13, 211, 7, 29, 71, 97, 1009, 11, 23, 331, 61, 53, 29927, 463, 3571, 17, 401, 129009091, 577, 1559, 745181, 4621, 43, 6217, 35839, 47, 2002867877, 5521, 101, 39756701, 79, 4057, 397760329, 369181, 68629840493971, 31, 241, 617671248800299, 3041, 14177
Offset: 1

Views

Author

N. J. A. Sloane, May 13 2007

Keywords

Comments

Read A001047 term-by-term, factorize each term, write down any primes not seen before.

Crossrefs

Extensions

a(41) and a(42) switched by Amiram Eldar, Jun 30 2023
Showing 1-5 of 5 results.