Floyd's triangle   lists the natural numbers in a right triangle aligned to the left where

 the first row is   1     (unity)
 successive rows start towards the left with the next number followed by successive naturals listing one more number than the line above.


The first few lines of a Floyd triangle looks like this:

 1
 2  3
 4  5  6
 7  8  9 10
11 12 13 14 15



Task

 Write a program to generate and display here the first   n   lines of a Floyd triangle. 
(Use   n=5   and   n=14   rows).
 Ensure that when displayed in a mono-space font, the numbers line up in vertical columns as shown and that only one space separates numbers of the last row.


: lastn ( rows -- n ) dup 1- * 2/ ;
: width ( n -- n )  s>f flog ftrunc f>s 2 + ;
 
: triangle ( rows -- )
  dup lastn 0 rot ( last 0 rows )
  0 do
    over cr
    i 1+ 0 do
      1+ swap 1+ swap
      2dup width u.r
    loop
    drop
  loop
  2drop ;
 