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 1-4 of 4 results.

A243010 Pseudoprimes to base 5 that are not squarefree.

Original entry on oeis.org

4, 124, 11476, 59356, 80476, 91636, 250876, 261964, 482516, 1385836, 1926676, 2428084, 2589796, 3743476, 4101796, 6797764, 9155476, 10701076, 10743436, 11263396, 13799836, 13859956, 15570556, 20396476
Offset: 1

Views

Author

Felix Fröhlich, Aug 18 2014

Keywords

Comments

Any term is divisible by the square of a base 5 Wieferich prime (A123692).
Intersection of A005936 and A013929. - Michel Marcus, Aug 21 2014

Links

Crossrefs

Cf. A005936, A123692, A158358, A243089, A243090, A244065.

Programs

  • PARI
    forcomposite(n=1, 1e9, if(Mod(5, n)^(n-1)==1, if(!issquarefree(n), print1(n, ", "))))

A243090 Pseudoprimes to base 8 that are not squarefree.

Original entry on oeis.org

9, 45, 63, 117, 153, 585, 2169, 4005, 9945, 13833, 17865, 27261, 33201, 36873, 40833, 57681, 69345, 69921, 95085, 140985, 155961, 161721, 171405, 186201, 189441, 192465, 203841, 240471, 242451, 244413, 316881, 321201, 406341, 481041, 482769, 488709, 501921
Offset: 1

Views

Author

Felix Fröhlich, Aug 18 2014

Keywords

Comments

Any member of the sequence is divisible by the square of a base 8 Wieferich prime, of which only three cases are known, namely 3, 1093 and 3511.
Intersection of A020137 and A013929. - Michel Marcus, Aug 21 2014

Links

Crossrefs

Cf. A020137, A158358, A243010, A243089, A244065.

Programs

  • PARI
    forcomposite(n=1, 1e9, if(Mod(8, n)^(n-1)==1, if(!issquarefree(n), print1(n, ", "))))

A306448 Pseudoprimes to base 9 that are not squarefree.

Original entry on oeis.org

4, 8, 28, 52, 121, 364, 532, 616, 1036, 1288, 3052, 3751, 4376, 4636, 4961, 5356, 6364, 7381, 8744, 11011, 11476, 12124, 15964, 19096, 19684, 21196, 21736, 24388, 26596, 29161, 31876, 32791, 37576, 40132, 45676, 47972, 53092, 61831, 67276, 72136, 80476, 80956, 86296
Offset: 1

Views

Author

Jianing Song, Feb 16 2019

Keywords

Comments

Numbers k that are not squarefree and satisfy 9^(k-1) == 1 (mod k).
Any term is divisible by the square of a base-9 Wieferich prime ({2} U {base-3 Wieferich primes} = {2} U A014127 = {2, 11, 1006003, ...}).
Intersection of A020138 and A013929.

Links

Crossrefs

Pseudoprimes to base b that are not squarefree: A158358 (b=2), A244065 (b=3), A243010 (b=5), A243089 (b=7), A243090 (b=8), this sequence (b=9), A306449 (b=10).
Cf. also A014127, A020138, A013929.

Programs

  • PARI
    for(n=1, 10^5, if(Mod(9, n)^(n-1)==1 && !issquarefree(n), print1(n, ", ")))

A306449 Pseudoprimes to base 10 that are not squarefree.

Original entry on oeis.org

9, 99, 657, 909, 1233, 11169, 13833, 19503, 20961, 23661, 51291, 69921, 90009, 99297, 109737, 139329, 203841, 237169, 256059, 321201, 339021, 346473, 460251, 475641, 686169, 760761, 927081, 1080801, 1621089, 1679931, 3100833, 3316941, 3845601, 3846051, 3942657, 4095081, 4281057
Offset: 1

Views

Author

Jianing Song, Feb 16 2019

Keywords

Comments

Numbers k that are not squarefree and satisfy 10^(k-1) == 1 (mod k).
Any term is divisible by the square of a base-10 Wieferich prime (A045616 = {3, 487, 56598313, ...}).
Intersection of A005939 and A013929.

Links

Crossrefs

Pseudoprimes to base b that are not squarefree: A158358 (b=2), A244065 (b=3), A243010 (b=5), A243089 (b=7), A243090 (b=8), A306448 (b=9), this sequence (b=10).
Cf. also A045616, A005939, A013929.

Programs

  • PARI
    for(n=1, 10^6, if(Mod(10, n)^(n-1)==1 && !issquarefree(n), print1(n, ", ")))
Showing 1-4 of 4 results.

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

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