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 11-16 of 16 results.

A090983 a(n) is the least nonsquare having square residues modulo each of the first n primes.

Original entry on oeis.org

2, 3, 6, 15, 15, 91, 246, 399, 399, 399, 3045, 3045, 21099, 41155, 43059, 182919, 182919, 182919, 182919, 860574, 860574, 8042479, 8042479, 11993466, 11993466, 11993466, 78278655, 78278655, 78278655, 78278655
Offset: 1

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Author

Don Reble, Feb 28 2004

Keywords

Crossrefs

Cf. A002189, A018883.

A001984 Erroneous version of A045535.

Original entry on oeis.org

7, 23, 71, 311, 479, 1559, 5711, 10559, 18191, 31391, 307271, 366791, 366791, 2155919
Offset: 1

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Author

Keywords

Links

A001985 Class numbers of quadratic fields.

Original entry on oeis.org

3, 7, 19, 25, 51, 109, 153, 213, 289, 1121, 1121, 1121, 3997, 7457, 12017, 12719, 20299, 24503, 24503, 25817, 25817, 128755, 128755, 219207, 456929, 456929, 761619, 883537
Offset: 3

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Author

N. J. A. Sloane

Keywords

References

  • D. H. Lehmer, E. Lehmer and D. Shanks, Integer sequences having prescribed quadratic character, Math. Comp., 24 (1970), 433-451.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

A001989 Class numbers associated with terms of A001988.

Original entry on oeis.org

1, 1, 5, 7, 7, 7, 9, 53, 73, 83, 83, 83, 157, 185, 185, 185, 185, 1927, 2295, 2273, 5313, 5313, 7173, 9529, 18545, 18545, 18545, 18545, 22635, 22635, 66011, 121725, 344909, 344909
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Crossrefs

Cf. A001988.

Programs

  • PARI
    isok(p, oddpn) = {forprime(q=3, oddpn, if (kronecker(p, q) != -kronecker(-1, q), return (0)); ); return (1); }
a(n) = {my(oddpn = prime(n+1)); forprime(p=3, , if (((p%8) == 7) &&  isok(p, oddpn), return (qfbclassno(-p*if(p%4>1, 4, 1)))););} \\ Michel Marcus, Oct 19 2017

Extensions

Better name from Sean A. Irvine, Mar 06 2013
Terms corrected by Sean A. Irvine, Mar 06 2013
Offset changed by Michel Marcus, Oct 19 2017

A001991 Class numbers associated with terms of A001990.

Original entry on oeis.org

2, 2, 2, 2, 2, 2, 2, 2, 46, 46, 46, 46, 46, 46, 406, 718, 950, 950, 950, 1698, 1698, 1698, 1698, 1698, 3990, 3990, 3990, 53510, 77970, 89478, 89478, 89478, 89478, 89478, 89478
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Crossrefs

Cf. A001990.

Programs

  • PARI
    isok(p, oddpn) = {forprime(q=3, oddpn, if (kronecker(p, q) != -kronecker(-2, q), return (0)); ); return (1); }
a(n) = {oddpn = prime(n+1); forprime(p=3, , if (((p%8) == 5) && isok(p, oddpn), return (qfbclassno(-8*p))); ); } \\ Michel Marcus, Oct 19 2017

Formula

a(n) = ClassNumber(-8*A001990(n)). - Sean A. Irvine, Mar 06 2013

Extensions

Better name from Sean A. Irvine, Mar 06 2013
Offset changed by Michel Marcus, Oct 19 2017

A002141 Class numbers of quadratic fields.

Original entry on oeis.org

1, 1, 5, 6, 7, 7, 9, 53, 60, 66, 83, 83, 136, 136, 185, 185, 185, 312, 312, 312, 3064, 3718, 3718, 3718, 8096, 9826, 12384, 16602, 16602, 16602, 16760, 16760, 182424, 323392, 323392, 323392, 323392
Offset: 3

Views

Author

N. J. A. Sloane

Keywords

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Previous Showing 11-16 of 16 results.

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

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