r"""
Python module for OEIS sequence number A007399.

Add 8, then reverse digits.

Examples of use.
-----------------------------------------------------------------------
>>> from a007399 import *
>>> print a007399_list(15)
[0, 8, 61, 96, 401, 904, 219, 722, 37, 54, 26, 43, 15, 32, 4]
>>> print a007399_offset
0
>>> for x in a007399_list_pairs(6):
...     print x
...
(0, 0)
(1, 8)
(2, 61)
(3, 96)
(4, 401)
(5, 904)
>>> print a007399(5)
904
-----------------------------------------------------------------------
"""

from itertools import islice, izip
from a003608 import a003608_gen

__all__ = ('a007399_offset', 'a007399_list', 'a007399_list_pairs', 'a007399', 'a003608_gen')
__author__ = 'Nick Hobson <nickh@qbyte.org>'

a007399_offset = offset = 0

def a007399_list(n):
    """Returns a list of the first n >= 0 terms."""
    if n < 0: raise ValueError, 'Input must be a non-negative integer'
    return list(islice(a003608_gen(8), n))

def a007399_list_pairs(n):
    """Returns a list of tuples (n, a(n)) of the first n >= 0 terms."""
    if n < 0: raise ValueError, 'Input must be a non-negative integer'
    return list(izip(xrange(offset, n+offset), a003608_gen(8)))

def a007399(n):
    """Returns the term with index n >= 0; offset 0."""
    if n < offset: raise ValueError, 'Input must be an integer >= offset = ' + str(offset)
    return list(islice(a003608_gen(8), n-offset, n-offset+1)).pop()