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.

Previous Showing 11-18 of 18 results.

A049202 Primes p whose order of primeness A049076(p) is >= 6.

Original entry on oeis.org

127, 709, 5381, 15299, 52711, 87803, 167449, 219613, 318211, 506683, 648391, 919913, 1128889, 1254739, 1471343, 1828669, 2269733, 2364361, 3042161, 3338989, 3509299, 4030889, 4535189, 5054303, 5823667, 6478961, 6816631
Offset: 1

Views

Author

Keywords

Comments

Union of A058322, A058324-A058328, A093046 etc.

Crossrefs

Programs

  • Maple
    map(ithprime@@4,select(isprime, [$1..137])); # Peter Luschny, Feb 17 2014
  • Mathematica
    Nest[ Prime, Range[35], 6] (* Robert G. Wilson v, Mar 15 2004 *)
  • PARI
    list(lim)=my(v=List(), q, r, s, t, u); forprime(p=2, lim, if(isprime(q++) && isprime(r++) && isprime(s++) && isprime(t++) && isprime(u++), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Feb 16 2017

Extensions

More terms from Robert G. Wilson v, Nov 10 2000
Name corrected by Sean A. Irvine, Jul 21 2021

A058325 Primes for which A049076(p) = 9.

Original entry on oeis.org

5381, 2269733, 17624813, 50728129, 77557187, 131807699, 259336153, 368345293, 440817757, 563167303, 751783477, 1107276647, 1170710369, 1367161723, 1760768239, 2062666783, 2323114841, 2458721501, 2621760397, 2860139341
Offset: 1

Views

Author

Robert G. Wilson v, Dec 12 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Nest[ Prime, Select[ Range[30], !PrimeQ[ # ] &], 8] (* Robert G. Wilson v, Mar 15 2004 *)

Formula

a(n) = A000040(A058324(n)). - R. J. Mathar, Jul 07 2012

A058326 Primes for which A049076(p) = 10.

Original entry on oeis.org

52711, 37139213, 326851121, 997525853, 1559861749, 2724711961, 5545806481, 8012791231, 9672485827, 12501968177, 16917026909, 25366202179, 26887732891, 31621854169, 41192432219, 48596930311, 55022031709, 58379844161
Offset: 1

Views

Author

Robert G. Wilson v, Dec 12 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Nest[ Prime, Select[ Range[30], !PrimeQ[ # ] &], 9] (* Robert G. Wilson v, Mar 15 2004 *)

Formula

a(n) = A000040(A058325(n)). - R. J. Mathar, Jul 07 2012

A058327 Primes for which A049076(p) = 11.

Original entry on oeis.org

648391, 718064159, 7069067389, 22742734291, 36294260117, 64988430769, 136395369829, 200147986693, 243504973489, 318083817907, 435748987787, 664090238153, 705555301183, 835122557939, 1099216100167, 1305164025929
Offset: 1

Views

Author

Robert G. Wilson v, Dec 12 2000

Keywords

Crossrefs

Programs

  • Mathematica
    Nest[ Prime, Select[ Range[30], !PrimeQ[ # ] &], 10] (* Robert G. Wilson v, Mar 15 2004 *)

Formula

a(n) = A000040(A058326(n)). - R. J. Mathar, Jul 07 2012

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

A135044 a(1)=1, then a(c) = p and a(p) = c, where c = T_c(r,k) and p = T_p(r,k), and where T_p contains the primes arranged in rows by the prime index chain and T_c contains the composites arranged in rows by the order of compositeness. See Formula.

Original entry on oeis.org

1, 4, 9, 2, 16, 7, 6, 13, 3, 19, 26, 17, 8, 23, 41, 5, 12, 67, 10, 29, 59, 37, 14, 83, 179, 11, 43, 331, 20, 47, 39, 109, 277, 157, 53, 431, 22, 1063, 31, 191, 15, 2221, 27, 61, 211, 71, 30, 599, 1787, 919, 241, 3001, 35, 73, 8527, 127, 1153, 79, 21, 19577, 44, 89, 283
Offset: 1

Views

Author

Katarzyna Matylla, Feb 11 2008

Keywords

Comments

Exchanges primes with composites, primeth primes with composith composites, etc.
Exchange the k-th prime of order j with the k-th composite of order j and vice versa.
Self-inverse permutation of positive integers.
If n is the composite number A236536(r,k), then a(n) is the corresponding prime A236542(r,k) at the same position (r,k). Vice versa, if n is the prime A236542(r,k), then a(n) is the corresponding composite A236536(r,k) at the same position. - Andrew Weimholt, Jan 28 2014
The original name for this entry did not produce this sequence, but instead A236854, which differs from this permutation for the first time at n=8, where A236854(8)=23, while here a(8)=13. - Antti Karttunen, Feb 01 2014

Examples

			From _Andrew Weimholt_, Jan 29 2014: (Start)
More generally, takes the primes organized in an array according to the sieving process described in the Fernandez paper:
        Row[1](n) = 2, 7, 13, 19, 23, ...
        Row[2](n) = 3, 17, 41, 67, 83, ...
        Row[3](n) = 5, 59, 179, ...
        Row[4](n) = 11, 277, ...
        Lets call this  T_p (n, k)
Also take the composites organized in a similar manner, except we use "composite" numbered positions in our sieve:
        Row[1](n) = 4, 6, 8, 10, 14, 20, 22, ...
        Row[2](n) = 9, 12, 15, 18, 24, ...
        Row[3](n) = 16, 21, 25, ...
        Lets call this T_c (n, k)
If we now take the natural numbers and swap each number (except for 1) with the number which holds the same spot in the other array, then we get the sequence: 1, 4, 9, 2, 16, 7, 6, 13, with for example a(8) = 13 (13 holds the same position in the 'prime' table as 8 does in the 'composite' table). (End)
		

Crossrefs

Programs

  • Maple
    A135044 := proc(n)
        if n = 1 then
            1;
        elif isprime(n) then
            idx := -1 ;
            for r from 1 do
                for c from 1 do
                    if A236542(r,c) = n then
                        idx := [r,c] ;
                    end if;
                    if A236542(r,c) >= n then
                        break;
                    end if;
                end do:
                if type(idx,list)  then
                    break;
                end if;
            end do:
            A236536(r,c) ;
        else
            idx := -1 ;
            for r from 1 do
                for c from 1 do
                    if A236536(r,c) = n then
                        idx := [r,c] ;
                    end if;
                    if A236536(r,c) >= n then
                        break;
                    end if;
                end do:
                if type(idx,list)  then
                    break;
                end if;
            end do:
            A236542(r,c) ;
        end if;
    end proc: # R. J. Mathar, Jan 28 2014
  • Mathematica
    Composite[n_Integer] := Block[{k = n + PrimePi@n + 1}, While[k != n + PrimePi@k + 1, k++ ]; k]; Compositeness[n_] := Block[{c = 1, k = n}, While[ !(PrimeQ@k || k == 1), k = k - 1 - PrimePi@k; c++ ]; c]; Primeness[n_] := Block[{c = 1, k = n}, While[ PrimeQ@k, k = PrimePi@k; c++ ]; c];
    ckj[k_, j_] := Select[ Table[Composite@n, {n, 10000}], Compositeness@# == j &][[k]]; pkj[k_, j_] := Select[ Table[Prime@n, {n, 3000}], Primeness@# == j &][[k]]; f[0]=0; f[1] = 1;
    f[n_] := If[ PrimeQ@ n, pn = Primeness@n; ckj[ Position[ Select[ Table[ Prime@ i, {i, 150}], Primeness@ # == pn &], n][[1, 1]], pn], cn = Compositeness@n; pkj[ Position[ Select[ Table[ Composite@ i, {i, 500}], Compositeness@ # == cn &], n][[1, 1]], cn]]; Array[f, 64] (* Robert G. Wilson v *)

Formula

a(1)=1, a(A236536(r,k))=A236542(r,k), a(A236542(r,k))=A236536(r,k)

Extensions

Edited, corrected and extended by Robert G. Wilson v, Feb 18 2008
Name corrected by Andrew Weimholt, Jan 29 2014

A283458 Primes for which A049076(p) = 14.

Original entry on oeis.org

3657500101, 12055296811267, 156740126985437, 575411103069067, 966399998477597, 1841803943951113, 4176603711876241, 6373890505436101, 7910004791442043, 10613343313176589, 15000987504638299, 23825707567607467, 25462803625208449, 30634679101122821, 41400950264534519, 49969246522326097
Offset: 1

Views

Author

Robert G. Wilson v, Mar 08 2017

Keywords

Comments

Also used Kim Walisch's primecount.

Crossrefs

Programs

  • Mathematica
    Nest[Prime, Select[Range[7], ! PrimeQ[#] &], 13]

Formula

a(n) = A000040(A093046(n)).

A283459 Primes for which A049076(p) = 15.

Original entry on oeis.org

88362852307, 392654585611999, 5519908106212193, 21034688742654437, 35843152090509943, 69532764058102673, 161191749822468689, 248761474969923757, 310467261969020581, 419776921940182991, 598644471430113247, 962125183414225879, 1029970322316321083, 1244984735583648473, 1695313841631390713
Offset: 1

Views

Author

Robert G. Wilson v, Mar 08 2017

Keywords

Comments

Also used Kim Walisch's primecount.

Crossrefs

Programs

  • Mathematica
    Nest[Prime, Select[Range[3], ! PrimeQ[#] &], 14]

Formula

a(n) = A000040(A283458(n)).
Previous Showing 11-18 of 18 results.