cells 0/1/2 are used for if/else condition
+                    set   1 to cell #0
>                    leave 0 in cell #1
>                    leave 0 in cell #2
> ++++ +++             initialize counter (cell #3) to 7
[                    use loop to set next four cells to 14/0/49
    > ++                 add   2 to cell #4
    >                    leave 0 in cell #5 (navigation stop condition)
    > ++++ +++           add   7 to cell #6
    <<< -                decrement counter at cell #3
]
>-                   set cell #4 to 13 (newline)
<,                   input main loop counter value into cell #3
[                    if main loop counter is not 0
    if direction cell in #0 is 1 then print sequence forward; otherwise print backward
    <[-]                 set #2 cell value to 0
    <[-]+                set #1 cell value to 1
    <                    navigate pointer to #0
    [             if #0 is 1 then (part of if/else construction)
      >>>>>>             navigate to the start of the sequence at #6
      [.>]               print the sequence forward
      <[<]               navigate back to #5
      <<<<-              navigate to #1 and set it to 0 to exit condition block (part of if/else construction)
    ]>                   (part of if/else construction) exit at #1 and navigate to #2 or exit at #0 and navigate to #1
    [             else   (entry position at #1)
      >>>>>              navigate to the sequence start at #6
      [>]                navigate to the last sequence element
      <[.<]              print the sequence backward; end at #5
      <<<<->             navigate to #1;set it to 0 and navigate to #2 (part of if/else construction)
    ]<<           end if; go back to #0 (part of if/else construction)
    as a result of if/else both #1 and #2 must be 0

    inverse value at #0 (1 to 0 / 0 to 1)
    [>+<[-]]      if #0 is true (is not 0) then set #1 to 1 and #0 to 0
    +             increment value at #0
    >[<->-]       if #1 is true (is not 0) then set #0 to 0 and #1 to 0
    inverse ends on #1

    >>>.              print newline taken from #4

    append new element to the end of the sequence
        >>                   go to the sequence start at #6
        [>]                  navigate to sequence end

        append 45 (minus) to the end of the sequence
        > +++++              set 5 to cell at the left; temporary counter
        [                    helper calculating 5*9 loop
            < +++++ ++++         append 9 to the cell at the right
            >-                   decrement temporary counter
        ]

        append the new element = previous element plus 1
        <<                   use previous cell as counter
        [
           >> +             go to the current cell and increment its value
           >  +             also make a copy to the cell at the right
           <<< -            decrement counter
        ]
        >>+                  increment the new value in the end of the sequence
        >                    copy value back to the previous cell in the sequence; use copy in the cell at the right as counter
        [
            <<<+             increment value in the previous cell
            >>>-             decrement counter value
        ]
    <[<]             put pointer to the beginning of the sequence (cell #6)
    <<-              decrement main loop counter in cell #3
]