r"""
Python module for OEIS sequence number A002491.

Smallest number of stones in Tchoukaillon (or Mancala, or Kalahari)
solitaire which make use of n-th hole.

Examples of use.
-----------------------------------------------------------------------
>>> from a002491 import *
>>> print a002491_list(15)
[1, 2, 4, 6, 10, 12, 18, 22, 30, 34, 42, 48, 58, 60, 78]
>>> print a002491_offset
1
>>> for x in a002491_list_pairs(6):
...     print x
...
(1, 1)
(2, 2)
(3, 4)
(4, 6)
(5, 10)
(6, 12)
>>> print a002491(5)
10
-----------------------------------------------------------------------
"""

__all__ = ('a002491_offset', 'a002491_list', 'a002491_list_pairs', 'a002491')
__author__ = 'Nick Hobson <nickh@qbyte.org>'

a002491_offset = offset = 1

def a002491_list(n):
    """Returns a list of the first n >= 0 terms of OEIS sequence A002491."""
    return [a002491(i) for i in xrange(offset, n+offset)]

def a002491_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(zip(xrange(offset, n+offset), a002491_list(n)))

def a002491(n):
    """Returns the term with index n >= 1; offset 1."""
    if n < offset: raise ValueError, 'Input must be an integer >= offset = ' + str(offset)
    x = n
    for i in xrange(n-1, 1, -1):
        x += (-x) % i
    return x