r"""
Python module for OEIS sequence number A048992.

Hannah Rollman's numbers: the numbers excluded from A048991.

Examples of use.
-----------------------------------------------------------------------
>>> from a048992 import *
>>> print a048992_list(12)
[12, 23, 31, 34, 41, 42, 45, 51, 52, 53, 56, 61]
>>> print a048992_offset
1
>>> for x in a048992_list_pairs(6):
...     print x
...
(1, 12)
(2, 23)
(3, 31)
(4, 34)
(5, 41)
(6, 42)
>>> print a048992_list_upto(41)
[12, 23, 31, 34, 41]
>>> print a048992(5)
41
-----------------------------------------------------------------------
"""

from itertools import islice, izip, takewhile, count

__all__ = ('a048992_offset', 'a048992_list', 'a048992_list_pairs', 'a048992_list_upto', 'a048992', 'a048992_gen')
__author__ = 'Nick Hobson <nickh@qbyte.org>'

a048992_offset = offset = 1


def a048992_gen():
    """Generator function for OEIS sequence A048992."""
    st = ''
    for n in count(1):
        t = str(n)
        if st.find(t) == -1:
            st += t
        else:
            yield n

def a048992_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(a048992_gen(), n))

def a048992_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), a048992_gen()))

def a048992_list_upto(m):
    """Returns a list of all terms not exceeding m > 0."""
    if m < 1: raise ValueError, 'Input must be a positive integer'
    return list(takewhile(lambda t: t <= m, a048992_gen()))

def a048992(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(a048992_gen(), n-offset, n-offset+1)).pop()