r"""
Python module for OEIS sequence numbers A057166.

A057166: Subtraction steps in Recaman's sequence A005132.

Examples of use.
-----------------------------------------------------------------------
>>> from a057166 import *
>>> print a057166_list(15)
[4, 8, 10, 12, 14, 16, 20, 22, 23, 25, 27, 29, 31, 35, 37]
>>> print a057166_offset
1
>>> for x in a057166_list_pairs(6):
...     print x
...
(1, 4)
(2, 8)
(3, 10)
(4, 12)
(5, 14)
(6, 16)
>>> print a057166(100)
208
-----------------------------------------------------------------------
"""

from itertools import islice, izip, count
from a057165 import a057165_gen

__all__ = ('a057166_offset', 'a057166_list', 'a057166_list_pairs', 'a057166', 'a057165_gen')
__author__ = 'Nick Hobson <nickh@qbyte.org>'

a057166_offset = offset = 1

def a057166_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(a057165_gen(False), n))

def a057166_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), a057165_gen(False)))

def a057166(n):
    """Returns the term with index n >= 1; offset 1."""
    if n < offset: raise ValueError, 'Input must be an integer >= offset = ' + str(offset)
    return list(islice(a057165_gen(False), n-1, n)).pop()