Create a sequence of numbers using the “Blum Blum Shub” pseudo-random
number generator:
Concatenate these numbers to create a string of infinite length.
Then,
For a positive integer , if no
substring of exists with a sum of
digits equal to , is defined to be zero. If at least
one substring of exists with a
sum of digits equal to , we define
, where is the starting position of the
earliest such substring.
For instance:
The substrings with respective sums of digits equal to
start at position ,
hence .
The substrings with respective sums of digits equal to
start at position ,
hence .
The substrings with respective sums of digits equal to
start at position ,
hence .
Note that substring starting at position
, has a sum of digits equal to
, but there was an earlier
substring (starting at position )
with a sum of digits equal to , so
, not .