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.

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

Links

Crossrefs

Cf. A049076, A007821, A049078, A049079, A049080, A049081, A058322, A058324, A058326, A058327, A058328, A093046, A006450.

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

Links

Crossrefs

Cf. A049076, A007821, A049078, A049079, A049080, A049081, A058322, A058324, A058325, A058327, A058328, A093046, A006450.

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

Links

Crossrefs

Cf. A049076, A007821, A049078, A049079, A049080, A049081, A058322, A058324, A058325, A058326, A058328, A093046, A006450.

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

A050436 Third-order composites.

Original entry on oeis.org

16, 21, 25, 26, 28, 33, 36, 38, 39, 42, 48, 49, 50, 52, 55, 56, 57, 60, 64, 68, 69, 70, 72, 74, 77, 78, 80, 84, 87, 88, 90, 93, 94, 95, 98, 100, 104, 105, 106, 110, 111, 115, 117, 118, 119, 121, 122, 124, 125, 126, 130, 133, 135, 138, 140, 141, 145, 146, 147
Offset: 1

Views

Author

Michael Lugo (mlugo(AT)thelabelguy.com), Dec 22 1999

Keywords

Examples

			C(C(C(8))) = C(C(15)) = C(25) = 38. So 38 is in the sequence.

Links

Crossrefs

Cf. A049076, A049077, A049078, A049079, A049080, A049081, A006450, A050435, A050438, ...

Programs

  • Maple
    C := remove(isprime,[$4..1000]): seq(C[C[C[C[n]]]],n=1..100);
  • Mathematica
    Nest[Values@ KeySelect[MapIndexed[First@ #2 -> #1 &, #], CompositeQ] &, Select[Range@ 150, CompositeQ], 2] (* Michael De Vlieger, Jul 22 2017 *)

Formula

Let C(n) be the n-th composite number, with C(1)=4. Then these are numbers C(C(C(n))).

Extensions

More terms from Asher Auel Dec 15 2000

A064960 The prime then composite recurrence; a(2n) = a(2n-1)-th prime and a(2n+1) = a(2n)-th composite and a(1) = 1.

Original entry on oeis.org

1, 2, 6, 13, 22, 79, 108, 593, 722, 5471, 6290, 62653, 69558, 876329, 951338, 14679751, 15692307, 289078661, 305618710, 6588286337, 6908033000, 171482959009, 178668550322, 5040266614919, 5225256019175, 165678678591359, 171068472492228, 6039923990345039
Offset: 1

Views

Author

Robert G. Wilson v, Oct 29 2001

Keywords

Links

Crossrefs

Cf. A007097, A006508 & A064961, see also A057450, A057451, A057452, A057453, A057456 & A057457 and A049076, A049077, A049078, A049079, A049080 & A049081.

Programs

  • Mathematica
    Composite[n_Integer] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; a = {1}; b = 1; Do[ If[ !PrimeQ[b], b = Prime[b], b = Composite[b]]; a = Append[a, b], {n, 1, 23}]; a
  • Python
    from functools import cache
from sympy import prime, composite
@cache
def A064960(n): return 1 if n == 1 else composite(A064960(n-1)) if n % 2 else prime(A064960(n-1)) # Chai Wah Wu, Jan 01 2022

Extensions

a(26)-a(28) from Chai Wah Wu, May 07 2018

A064961 Composite-then-prime recurrence; a(2n) = a(2n-1)-th composite and a(2n+1) = a(2n)-th prime and a(1) = 1.

Original entry on oeis.org

1, 4, 7, 14, 43, 62, 293, 366, 2473, 2892, 26317, 29522, 344249, 376259, 5429539, 5831545, 101291779, 107457490, 2198218819, 2310909505, 54720307351, 57128530327, 1543908890351, 1603146693999, 48871886538151, 50527531769529, 1720466016680911, 1772475453490311
Offset: 1

Views

Author

Robert G. Wilson v, Oct 29 2001

Keywords

Links

Crossrefs

Cf. A007097, A006508 & A064960, see also A057450, A057451, A057452, A057453, A057456 & A057457 and A049076, A049077, A049078, A049079, A049080 & A049081.

Programs

  • Mathematica
    Composite[n_Integer] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; a = {1, 4}; b = 4; Do[ If[ !PrimeQ[b], b = Prime[b], b = Composite[b]]; a = Append[a, b], {n, 1, 23}]; a

Extensions

a(24)-a(26) corrected and a(27)-a(28) added by Chai Wah Wu, Aug 22 2018

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.

Links

Crossrefs

Cf. A049076, A006450, A114537, A007821, A049078, A049079, A049080, A049081, A058322, A058324,Cf. A058325, A058326, A058327, A058328, A093046, A283459.

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.

Links

Crossrefs

Cf. A049076, A006450, A114537, A007821, A049078, A049079, A049080, A049081, A058322, A058324, A058325, A058326, A058327, A058328, A093046, A283458.

Programs

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

Formula

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

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