Sources of true random sequences                                                
        0) AVOID /dev/random /dev/urandom:

        The kernel random-number generator is designed to produce
        a small amount of high-quality seed material to seed a
        cryptographic pseudo- random number generator (CPRNG). It
        is designed for security, not speed, and is poorly suited
        to generating large amounts of random data. Users should be
        very economical in the amount of seed material that they
        read from /dev/urandom (and /dev/random); unnecessarily
        reading large quantities of data from this device will have
        a negative impact on other users of the device.
        -- excerpt from man urandom (linux)

        Applications retrieve random bytes by reading /dev/random
        or /dev/uran- dom. The /dev/random interface returns random
        bytes only when suffi- cient amount of entropy has been
        collected. If there is no entropy to produce the requested
        number of bytes, /dev/random blocks until more entropy can
        be obtained. Non-blocking I/O mode can be used to disable
        the blocking behavior. The /dev/random interface also
        supports poll(2). Note that using poll(2) does not increase
        the speed at which random numbers can be read.
        -- excerpt from man urandom (Solaris)

        1) http://www.fourmilab.ch/hotbits/

        2) http://random.irb.hr/index.php

        3) https://www.random.org/

        4) perl module: 
           Net::Random - get random data from online sources
           Sample output, 5 integers (min, max vary):
            From fourmilab.ch   : 600 1785 384 1466 1212
            From qrng.anu.edu.au: 2498 2234 2071 2573 2868
            From random.org     : 7014 5940 5911 6289 3246