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 1-10 of 35 results. Next

A057847 Primes p whose order of primeness A078442(p) is at least 10.

Original entry on oeis.org

648391, 9737333, 174440041, 718064159, 3657500101, 7069067389, 16123689073, 22742734291, 36294260117, 64988430769, 88362852307, 136395369829, 175650481151, 200147986693, 243504973489, 318083817907, 414507281407
Offset: 1

Views

Author

Robert G. Wilson v, Nov 10 2000

Keywords

Crossrefs

Programs

Formula

a(n) = prime(A057851(n)). - Andrew Howroyd, Nov 17 2024

Extensions

Name clarified by Andrew Howroyd, Nov 17 2024

A057849 Primes p whose order of primeness A078442(p) is at least 7.

Original entry on oeis.org

709, 5381, 52711, 167449, 648391, 1128889, 2269733, 3042161, 4535189, 7474967, 9737333, 14161729, 17624813, 19734581, 23391799, 29499439, 37139213, 38790341, 50728129, 56011909, 59053067, 68425619, 77557187, 87019979, 101146501, 113256643, 119535373, 127065427
Offset: 1

Views

Author

Robert G. Wilson v, Nov 10 2000

Keywords

Crossrefs

Programs

  • Maple
    a:= ithprime@@7;
    seq(a(n), n=1..30);  # Alois P. Heinz, Jun 14 2015
  • Mathematica
    Nest[ Prime, Range[35], 7] (* Robert G. Wilson v, Mar 15 2004 *)
  • PARI
    list(lim)=my(v=List(), q, r, s, t, u, vv); forprime(p=2, lim, if(isprime(q++) && isprime(r++) && isprime(s++) && isprime(t++) && isprime(u++) && isprime(vv++), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Feb 16 2017

Extensions

Name clarified by Andrew Howroyd, Nov 17 2024

A057850 Primes p whose order of primeness A078442(p) is at least 8.

Original entry on oeis.org

5381, 52711, 648391, 2269733, 9737333, 17624813, 37139213, 50728129, 77557187, 131807699, 174440041, 259336153, 326851121, 368345293, 440817757, 563167303, 718064159, 751783477, 997525853, 1107276647, 1170710369, 1367161723
Offset: 1

Views

Author

Robert G. Wilson v, Nov 10 2000

Keywords

Comments

Union of A058325-A058328, A093046 etc. - R. J. Mathar, Jul 07 2012

Crossrefs

Programs

  • Mathematica
    Nest[ Prime, Range[35], 8] (* Robert G. Wilson v, Mar 15 2004 *)
  • PARI
    list(lim)=my(v=List(), q, r, s, t, u, vv, w); forprime(p=2, lim, if(isprime(q++) && isprime(r++) && isprime(s++) && isprime(t++) && isprime(u++) && isprime(vv++) && isprime(w++), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Feb 19 2017

Formula

a(n) = A049090(A049090(n)). - James G. Merickel, Feb 14 2010
a(n) = A000040(A057849(n)). - R. J. Mathar, Jul 07 2012

Extensions

Name clarified by Andrew Howroyd, Nov 17 2024

A057851 Primes p whose order of primeness A078442(p) is at least 9.

Original entry on oeis.org

52711, 648391, 9737333, 37139213, 174440041, 326851121, 718064159, 997525853, 1559861749, 2724711961, 3657500101, 5545806481, 7069067389, 8012791231, 9672485827, 12501968177, 16123689073, 16917026909, 22742734291
Offset: 1

Views

Author

Robert G. Wilson v, Nov 10 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Nest[ Prime, Range[35], 9] (* Robert G. Wilson v, Mar 15 2004 *)
  • PARI
    list(lim)=my(v=List(), q, r, s, t, u, vv, w, x); forprime(p=2, lim, if(isprime(q++) && isprime(r++) && isprime(s++) && isprime(t++) && isprime(u++) && isprime(vv++) && isprime(w++) && isprime(x++), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Feb 19 2017

Extensions

Name clarified by Andrew Howroyd, Nov 17 2024

A058332 Primes p whose order of primeness A078442(p) is at least 11.

Original entry on oeis.org

9737333, 174440041, 3657500101, 16123689073, 88362852307, 175650481151, 414507281407, 592821132889, 963726515729, 1765037224331, 2428095424619, 3809491708961, 4952019383323, 5669795882633, 6947574946087, 9163611272327
Offset: 1

Views

Author

Robert G. Wilson v, Dec 12 2000

Keywords

Crossrefs

Programs

Formula

a(n) = prime(A057847(n)). - Andrew Howroyd, Nov 17 2024

Extensions

Name clarified by Andrew Howroyd, Nov 17 2024

A093047 Primes p whose order of primeness A078442(p) is at least 12.

Original entry on oeis.org

174440041, 3657500101, 88362852307, 414507281407, 2428095424619, 4952019383323, 12055296811267, 17461204521323, 28871271685163, 53982894593057, 75063692618249, 119543903707171, 156740126985437, 180252380737439, 222334565193649
Offset: 1

Views

Author

Robert G. Wilson v, Mar 15 2000

Keywords

Comments

Primes p whose primeness is > 12: 3657500101, 88362852307, 2428095424619, 12055296811267, 75063692618249, 156740126985437, ..., . - Robert G. Wilson v, Mar 15 2000

Crossrefs

Programs

Formula

a(n) = A058332(prime(n)). - Andrew Howroyd, Nov 17 2024

Extensions

Name clarified by Andrew Howroyd, Nov 17 2024

A333353 Primes p whose order of primeness A078442(p) is prime.

Original entry on oeis.org

3, 5, 17, 31, 41, 59, 67, 83, 109, 157, 179, 191, 211, 241, 283, 331, 353, 367, 401, 431, 461, 509, 547, 563, 587, 599, 617, 709, 739, 773, 797, 859, 877, 919, 967, 991, 1031, 1087, 1153, 1171, 1201, 1217, 1297, 1409, 1433, 1447, 1471, 1499, 1523, 1597, 1621
Offset: 1

Views

Author

Alois P. Heinz, Mar 15 2020

Keywords

Examples

			31 is a term: 31 -> 11 -> 5 -> 3 -> 2 -> 1, five (a prime number of) steps "->" = pi = A000720.
		

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember;
          `if`(isprime(n), 1+b(numtheory[pi](n)), 0)
        end:
    a:= proc(n) option remember; local p;
          p:= `if`(n=1, 1, a(n-1));
          do p:= nextprime(p);
             if isprime(b(p)) then break fi
          od; p
        end:
    seq(a(n), n=1..55);
  • Mathematica
    b[n_] := b[n] = If[!PrimeQ[n], 0, 1+b[PrimePi[n]]];
    okQ[n_] := PrimeQ[n] && PrimeQ[b[n]];
    Select[Range[2000], okQ] (* Jean-François Alcover, May 30 2022 *)

Formula

{ p in primes : A078442(p) is prime }.
a(n) = prime(A333364(n)).

A333364 Indices of primes p whose order of primeness A078442(p) is prime.

Original entry on oeis.org

2, 3, 7, 11, 13, 17, 19, 23, 29, 37, 41, 43, 47, 53, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283
Offset: 1

Views

Author

Alois P. Heinz, Mar 16 2020

Keywords

Comments

All terms are prime.

Examples

			11 is a term: prime(11) = 31 -> 11 -> 5 -> 3 -> 2 -> 1, five (a prime number of) steps "->" = pi = A000720.
		

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember;
          `if`(isprime(n), 1+b(numtheory[pi](n)), 0)
        end:
    a:= proc(n) option remember; local p;
          p:= `if`(n=1, 1, a(n-1));
          do p:= nextprime(p);
             if isprime(b(p)+1) then break fi
          od; p
        end:
    seq(a(n), n=1..62);
  • Mathematica
    b[n_] := b[n] = If[PrimeQ[n], 1 + b[PrimePi[n]], 0];
    a[n_] := a[n] = Module[{p}, p = If[n == 1, 1, a[n - 1]];
       While[True, p = NextPrime[p]; If[PrimeQ[b[p] + 1], Break[]]]; p];
    Table[a[n], {n, 1, 62}] (* Jean-François Alcover, Sep 14 2022, after Alois P. Heinz *)

Formula

{ p in primes : A049076(p) is prime }.
a(n) = pi(A333353(n)), with pi = A000720.

A094722 Primes p whose order of primeness A078442(p) is at least 13.

Original entry on oeis.org

3657500101, 88362852307, 2428095424619, 12055296811267, 75063692618249, 156740126985437
Offset: 1

Views

Author

Robert G. Wilson v, May 22 2004

Keywords

Crossrefs

Programs

  • Mathematica
    Nest[ Prime, Range[35], 13]

Formula

a(n) = prime(A093047(n)). - Andrew Howroyd, Nov 17 2024

Extensions

a(6) from Robert G. Wilson v, May 22 2004
Name clarified by Andrew Howroyd, Nov 17 2024

A007097 Primeth recurrence: a(n+1) = a(n)-th prime.

Original entry on oeis.org

1, 2, 3, 5, 11, 31, 127, 709, 5381, 52711, 648391, 9737333, 174440041, 3657500101, 88362852307, 2428095424619, 75063692618249, 2586559730396077, 98552043847093519, 4123221751654370051, 188272405179937051081, 9332039515881088707361, 499720579610303128776791, 28785866289100396890228041
Offset: 0

Views

Author

Keywords

Comments

A007097(n) = Min {k : A109301(k) = n} = the first k whose rote height is n, the level set leader or minimum inverse function corresponding to A109301. - Jon Awbrey, Jun 26 2005
Lubomir Alexandrov informs me that he studied this sequence in his 1965 notebook. - N. J. A. Sloane, May 23 2008
a(n) is the Matula-Goebel number of the rooted path tree on n+1 vertices. The Matula-Goebel number of a rooted tree can be defined in the following recursive manner: to the one-vertex tree there corresponds the number 1; to a tree T with root degree 1 there corresponds the t-th prime number, where t is the Matula-Goebel number of the tree obtained from T by deleting the edge emanating from the root; to a tree T with root degree m>=2 there corresponds the product of the Matula-Goebel numbers of the m branches of T. - Emeric Deutsch, Feb 18 2012
Conjecture: log(a(1))*log(a(2))*...*log(a(n)) ~ a(n). - Thomas Ordowski, Mar 26 2015

References

  • Lubomir Alexandrov, unpublished notes, circa 1960.
  • L. Longeri, Towards understanding nature and the aesthetics of prime numbers, https://www.longeri.org/prime/nature.html [Broken link, but leave the URL here for historical reasons]
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Row 1 of array A114537.
Left edge of tree A227413, right edge of A246378.
Cf. A078442, A109082 (left inverses).
Subsequence of A245823.

Programs

  • GAP
    P:=Filtered([1..60000],IsPrime);;
    a:=[1];; for n in [2..10] do a[n]:=P[a[n-1]]; od; a; # Muniru A Asiru, Dec 22 2018
  • Haskell
    a007097 n = a007097_list !! n
    a007097_list = iterate a000040 1  -- Reinhard Zumkeller, Jul 14 2013
    
  • Maple
    seq((ithprime@@n)(1),n=0..10); # Peter Luschny, Oct 16 2012
  • Mathematica
    NestList[Prime@# &, 1, 16] (* Robert G. Wilson v, May 30 2006 *)
  • PARI
    print1(p=1);until(,print1(","p=prime(p)))  \\ M. F. Hasler, Oct 09 2011
    

Formula

A049084(a(n+1)) = a(n). - Reinhard Zumkeller, Jul 14 2013
a(n)/a(n-1) ~ log(a(n)) ~ prime(n). - Thomas Ordowski, Mar 26 2015
a(n) = prime^{[n]}(1), with the prime function prime(k) = A000040(k), with a(0) = 1. See the name and the programs. - Wolfdieter Lang, Apr 03 2018
Sum_{n>=1} 1/a(n) = A292667. - Amiram Eldar, Oct 15 2020

Extensions

a(15) corrected and a(16)-a(17) added by Paul Zimmermann
a(18)-a(19) found by David Baugh using a program by Xavier Gourdon and Andrey V. Kulsha, Oct 25 2007
a(20)-a(21) found by Andrey V. Kulsha using a program by Xavier Gourdon, Oct 02 2011
a(22) from Henri Lifchitz, Oct 14 2014
a(23) from David Baugh using Kim Walisch's primecount, May 16 2016
Showing 1-10 of 35 results. Next