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 1-3 of 3 results.

A153580 Terms of A083737 which are not Carmichael numbers (A002997).

Original entry on oeis.org

721801, 873181, 4504501, 8646121, 9006401, 9863461, 10403641, 12322133, 14609401, 15913261, 18595801, 18736381, 20234341, 21397381, 22066201, 22369621, 22885129, 25326001, 25696133, 28312921, 36307981, 42702661
Offset: 1

Views

Author

Ray Chandler & Artur Jasinski, Dec 28 2008

Keywords

Links

Crossrefs

Cf. A002997, A083737, A122780, A153508, A153513, A153514, A153515, A153519, A153581.

Programs

  • Mathematica
    Select[Range[5*10^7], ! PrimeQ[ # ] && PowerMod[2, # - 1, # ] == 1 && PowerMod[3, # - 1, # ] == 1 && PowerMod[5, # - 1, # ] == 1 && Mod[ #, CarmichaelLambda[ # ]] != 1 &] (* Ray Chandler, Dec 28 2008 *)

A153581 Pseudoprimes to bases 2,3,5 and 7 which are not Carmichael numbers (A002997).

Original entry on oeis.org

721801, 8646121, 10403641, 22885129, 36307981, 42702661, 46094401, 48064021, 52204237, 79398901, 80918281, 81954133, 114329881, 116151661, 143168581, 170782921, 188985961, 217145881, 220531501, 282707461, 299671921, 303373801, 326695141, 353815801, 361307521
Offset: 1

Views

Author

Ray Chandler & Artur Jasinski, Dec 28 2008

Keywords

Comments

Terms congruent to 5 (mod 6): 468950021, 493108481, 659846021, 5936122901, 8144063621, ... - Robert G. Wilson v, Sep 03 2014
Terms not congruent to 1 (mod 12): 468950021, 493108481, 643767931, 659846021, 773131927, 5779230451, 5936122901, 7294056727, 8144063621, 9671001451, ... - Robert G. Wilson v, Sep 03 2014

Links

Crossrefs

Cf. A002997, A083737, A122780, A153508, A153513, A153514, A153515, A153519, A153580.

Programs

  • Mathematica
    fQ[n_] := ! PrimeQ[n] && PowerMod[2, n - 1, n] == 1 && PowerMod[3, n - 1, n] == 1 && PowerMod[5, n - 1, n] == 1 && PowerMod[7, n - 1, n] == 1 && Mod[n, CarmichaelLambda[n]] != 1; Select[ Range[ 365000000], fQ] (* Ray Chandler, Dec 28 2008; corrected by Robert G. Wilson v, Sep 01 2014 *)

Extensions

Terms a(8) and onward from Robert G. Wilson v, Sep 01 2014

A153519 Nonprime numbers k such that 10^k == 10 (mod k) and are not Carmichael numbers.

Original entry on oeis.org

1, 6, 9, 10, 15, 18, 30, 33, 45, 55, 90, 91, 99, 165, 246, 259, 370, 385, 451, 481, 495, 505, 657, 703, 715, 909, 1035, 1045, 1233, 1626, 2035, 2409, 2981, 3333, 3367, 3585, 4005, 4141, 4187, 4521, 4545, 5005, 5461, 6533, 6541, 6565, 7107, 7471, 7777, 8149
Offset: 1

Views

Author

Artur Jasinski, Dec 28 2008

Keywords

Comments

Old name: Members of A121014 which are not Carmichael numbers A002997.

Links

Crossrefs

Cf. A002997, A122780, A153508, A153513, A153514, A153515.

Programs

  • Mathematica
    Select[Range[8000], !PrimeQ[#] && PowerMod[10, #, #] == Mod[10, #] && !(# > 1 && Divisible[# - 1, CarmichaelLambda[#]]) &] (* Amiram Eldar, Mar 19 2020 *)
  • PARI
    isok(n) = !isprime(n) && !is_A002997(n) && (Mod(10^n, n) == Mod(10, n)); \\ Michel Marcus, Nov 06 2013

Extensions

New name from Michel Marcus, Nov 06 2013
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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