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Prime Factors | q: 0 0 0 | Prime Exponents

`q: y` is the list of prime factors of a positive integer argument`y` .`` For example:

       y=: 105600
       q: y
    2 2 2 2 2 2 2 3 5 5 11
       */q: y
    105600
       $ q: 1
    0
       */q: 1
    1
       q: b. _1
    */

If`x` is positive and finite,`x q: y` is the list of exponents in the prime decomposition of positive integer`y`,`` based upon the first`x` primes; if`x` is`_` ,`` a sufficient number of primes is used.
If`x` is negative and finite,`x q: y` is a 2-row table of the last`|x` primes and exponents in the prime factorization of`y` ;`` if`x` is `__` ,`` a sufficient number of primes is used. For example:

       2 q: 700
    2 0
       10 q: 700
    2 0 2 1 0 0 0 0 0 0
       _ q: 700
    2 0 2 1

       ~.@q: 700                            NB. Distinct prime factors
    2 5 7

       +/"1@=@q: 700                        NB. Exponents in prime factorization
    2 2 1

       __ q: 700
    2 5 7
    2 2 1

       __ q: !20x
     2 3 5 7 11 13 17 19
    18 8 4 2  1  1  1  1

       y=: 100
       e=: _&q:                             NB. Completed list of exponents
       (e ; +:&.e ; -:&.e ; %&3&.e)y        NB. Exponents, square, sqrt, cube root
    +-----+-----+--+-------+
    |2 0 2|10000|10|4.64159|
    +-----+-----+--+-------+

       V=: /@,:                             NB. For vectors of disparate lengths

       12 (+V&.e; -V&.e; >.V&.e; <.V&.e) y  NB. Product, quotient, LCM, GCD
    +----+----+---+-+
    |1200|0.12|300|4|
    +----+----+---+-+

       totient=: * -.@%@~.&.q:              NB. Euler's totient function
       totient 700
    240

       +/ 1 = 700 +. i.700
    240

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