Programming Praxis

2 Responses to “Fetch OEIS Sequences”

1. Alex B. said

   May 24, 2019 at 9:05 AM

   Since OEIS offers a nice JSON format, I thought I’d take advantage:

   #! /usr/bin/env python3
   
   import sys
   
   import requests
   
   OEIS_URL = 'https://oeis.org/search'
   
   def get_seq(seq_name):
       """Fetch and return an OEIS sequence in JSON format"""
       params = {
           'q': f'id:{seq_name}',
           'fmt': 'json',
           }
       response = requests.get(OEIS_URL, params)
       response.raise_for_status()
       return response.json()
   
   def extract_seq(seq_json):
       """Extract and return the sequences from OEIS JSON data"""
       results = seq_json['results']
       seqs = dict()
       for result in results:
           number = result['number']
           a_id = f'A{number:06}'
           seqs[a_id] = result['data']
       if seqs:
           return seqs
       else:
           return None
   
   if __name__ == '__main__':
       seq_id = sys.argv[1]
       seq_json = get_seq(seq_id)
       seq_data = extract_seq(seq_json)
       if seq_data is not None:
           for seq in seq_data:
               print(f'{seq}: {seq_data[seq]}')
       else:
           print('No sequence found')
   

   get_seq adds the ‘id:’ prefix to the search term, so only one sequence is fetched. Next step is to add command line switches to control that behaviour, so multiple sequences can be fetched at once.
2. Daniel said

   June 30, 2019 at 12:28 AM

   Here’s a solution in Python.

   import json
   import sys
   import urllib.request
   
   assert len(sys.argv) == 2, 'ID argument required'
   url = f'https://oeis.org/search?q=id:{sys.argv[1]}&fmt=json'
   with urllib.request.urlopen(url) as u:
       body = u.read()
   data = json.loads(body)['results'][0]['data'].split(',')
   print('\n'.join(data))
   

   Example Usage:

   $ python oeis.py A000045
   0
   1
   1
   2
   3
   5
   8
   13
   21
   34
   55
   ...