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# Local copy of Sloane On-Line Encyclopedia of Integer Sequences

The SloaneEncyclopedia object provides access to a local copy of the database containing only the sequences and their names. To use this you must download and install the database using `SloaneEncyclopedia.install()`, or `SloaneEncyclopedia.install_from_gz()` if you have already downloaded the database manually.

To look up a sequence, type

    sage: SloaneEncyclopedia[60843]               # optional - sloane_database
    [1, 6, 21, 107]

To get the name of a sequence, type

    sage: SloaneEncyclopedia.sequence_name(1)     # optional - sloane_database
    'Number of groups of order n.'

To search locally for a particular subsequence, type

    sage: SloaneEncyclopedia.find([1,2,3,4,5], 1)    # optional - sloane_database
    [(15, [1, 2, 3, 4, 5, 7, 7, 8, 9, 11, 11, 13, 13, 16, 16, 16, 17, 19, 19, 23, 23, 23, 23, 25, 25, 27, 27, 29, 29, 31, 31, 32, 37, 37, 37, 37, 37, 41, 41, 41, 41, 43, 43, 47, 47, 47, 47, 49, 49, 53, 53, 53, 53, 59, 59, 59, 59, 59, 59, 61, 61, 64, 64, 64, 67, 67, 67, 71, 71, 71, 71, 73])]

The default maximum number of results is 30, but to return up to 100, type

    sage: SloaneEncyclopedia.find([1,2,3,4,5], 100)    # optional - sloane_database
    [(15, [1, 2, 3, 4, 5, 7, 7, 8, 9, 11, 11, ...

Results in either case are of the form [ (number, list) ].

See also

- If you want to get more informations relative to a sequence (references, links, examples, programs, ...), you can use the On-Line Encyclopedia of Integer Sequences provided by the `OEIS` module.
- Some infinite OEIS sequences are implemented in Sage, via the `sloane_functions` module.

AUTHORS:

- Steven Sivek (2005-12-22): first version
- Steven Sivek (2006-02-07): updated to correctly handle the new search form on the Sloane website, and it’s now also smarter about loading the local database in that it doesn’t convert a sequence from string form to a list of integers until absolutely necessary. This seems to cut the loading time roughly in half.
- Steven Sivek (2009-12-22): added the SloaneEncyclopedia functions install() and install_from_gz() so users can get the latest versions of the OEIS without having to get an updated spkg; added sequence_name() to return the description of a sequence; and changed the data type for elements of each sequence from int to Integer.
- Thierry Monteil (2012-02-10): deprecate dead code and update related doc and tests.

## Classes and methods

class `sage.databases.sloane.``SloaneEncyclopediaClass`

  A local copy of the Sloane Online Encyclopedia of Integer Sequences that contains only the sequence numbers and the sequences themselves.

  `find`(seq, maxresults=30)

    Return a list of all sequences which have seq as a subsequence, up to maxresults results. Sequences are returned in the form (number, list).

    INPUT:

    - `seq` - list
    - `maxresults` - int

    OUTPUT: list of 2-tuples (i, v), where v is a sequence with seq as a subsequence.

  `install`(oeis_url='http://oeis.org/stripped.gz', names_url='http://oeis.org/names.gz', overwrite=False)

    Download and install the online encyclopedia, raising an IOError if either step fails.

    INPUT:

    - `oeis_url` - string (default: “http://oeis.org...”) The URL of the stripped.gz encyclopedia file.
    - `names_url` - string (default: “http://oeis.org...”) The URL of the names.gz encyclopedia file. If you do not want to download this file, set names_url=None.
    - `overwrite` - boolean (default: False) If the encyclopedia is already installed and overwrite=True, download and install the latest version over the installed one.
  `install_from_gz`(stripped_file, names_file, overwrite=False)

    Install the online encyclopedia from a local stripped.gz file.

    INPUT:

    - `stripped_file` - string. The name of the stripped.gz OEIS file.
    - `names_file` - string. The name of the names.gz OEIS file, or None if the user does not want it installed.
    - `overwrite` - boolean (default: False) If the encyclopedia is already installed and overwrite=True, install ‘filename’ over the old encyclopedia.
  `load`()

    Load the entire encyclopedia into memory from a file. This is done automatically if the user tries to perform a lookup or a search.

  `sequence_name`(N)

    Return the name of sequence N in the encyclopedia. If sequence N does not exist, return ‘’. If the names database is not installed, raise an IOError.

    INPUT:

    - `N` - int

    OUTPUT: string

    EXAMPLES:

    sage: SloaneEncyclopedia.sequence_name(1) # optional - sloane_database ‘Number of groups of order n.’

  `unload`()

    Remove the database from memory.

`sage.databases.sloane.``copy_gz_file`(gz_source, bz_destination)

  Decompress a gzipped file and install the bzipped verson. This is used by SloaneEncyclopedia.install_from_gz to install several gzipped OEIS database files.

  INPUT:

  - `gz_source` - string. The name of the gzipped file.
  - `bz_destination` - string. The name of the newly compressed file.

`sage.databases.sloane.``parse_sequence`(text='')

  This internal function was only used by the sloane_find function, which is now deprecated.

  TESTS::
    sage: from sage.databases.sloane import parse_sequence sage: parse_sequence() doctest:...: DeprecationWarning: The function parse_sequence is not used anymore (2012-01-01). See http://trac.sagemath.org/10358 for details.

`sage.databases.sloane.``sloane_find`(list=[], nresults=30, verbose=True)

  This function is broken. It is replaced by the `OEIS` module.

  Type `oeis?` for more information.

  TESTS:

      sage: sloane_find([1,2,3])
      doctest:...: DeprecationWarning: The function sloane_find is deprecated. Use oeis() instead (2012-01-01).
      See http://trac.sagemath.org/10358 for details.

`sage.databases.sloane.``sloane_sequence`(number=1, verbose=True)

  This function is broken. It is replaced by the `OEIS` module.

  Type `oeis?` for more information.

  TESTS:

      sage: sloane_sequence(123)
      doctest:...: DeprecationWarning: The function sloane_sequence is deprecated. Use oeis() instead (2012-01-01).
      See http://trac.sagemath.org/10358 for details.

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