Sum digits till Square
Perl 6, 60 bytes



{$/=[$^x,*.polymod($^y xx*).sum*($y-1)...($y-1)²];$/-1,|$/}


Expanded:

{    # bare block lambda with placeholder parameters ｢$x｣ ｢$y｣

  $/ = [          # store in ｢$/｣ ( so that we don't have to declare it )

    # generate a sequence

    $^x,          # declare first parameter, and seed sequence generator

    # Whatever lambda

    *\            # the parameter to this lambda

    .polymod(     # broken down with a list of moduli

      $^y         # declare second parameter of the outer block lambda
      xx *        # an infinite list of copies of it

    )
    .sum
    *
    ( $y - 1 )

    # end of Whatever lambda

    ...           # repeat until it reaches

    ( $y - 1 )²
  ];

  # returns
  $/ - 1,         # count of values minus one
  |$/             # Slip ｢|｣ the list into the result
}


Usage:

# store it in the lexical namespace so that it is easier to understand
my &amp;code = {$/=[$^x,*.polymod($^y xx*).sum*($y-1)...($y-1)²];$/-1,|$/}

say code  739,  7; # (2 739 42 36)
say code 1712, 19; # (3 1712 360 648 324)