r"""
Python module for OEIS sequence number A007398.

Add 7, then reverse digits.

Examples of use.
-----------------------------------------------------------------------
>>> from a007398 import *
>>> print a007398_list(15)
[0, 7, 41, 84, 19, 62, 96, 301, 803, 18, 52, 95, 201, 802, 908]
>>> print a007398_offset
0
>>> for x in a007398_list_pairs(6):
...     print x
...
(0, 0)
(1, 7)
(2, 41)
(3, 84)
(4, 19)
(5, 62)
>>> print a007398(5)
62
-----------------------------------------------------------------------
"""

from itertools import islice, izip
from a003608 import a003608_gen

__all__ = ('a007398_offset', 'a007398_list', 'a007398_list_pairs', 'a007398', 'a003608_gen')
__author__ = 'Nick Hobson <nickh@qbyte.org>'

a007398_offset = offset = 0

def a007398_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(7), n))

def a007398_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(7)))

def a007398(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(7), n-offset, n-offset+1)).pop()