Floyd's triangle

func floyd(rows, n=1) {
    var max = Math.range_sum(1, rows)
    var widths = (max-rows .. max-1 -> map{.+n->to_s.len})
    { |r|
        say %'#{1..r -> map{|i| "%#{widths[i-1]}d" % n++}.join(" ")}'
    } << 1..rows
}

floyd(5)     # or: floyd(5, 88)
floyd(14)    # or: floyd(14, 900)

Output:

 1
 2  3
 4  5  6
 7  8  9 10
11 12 13 14 15
 1
 2  3
 4  5  6
 7  8  9 10
11 12 13 14 15
16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31 32 33 34 35 36
37 38 39 40 41 42 43 44  45
46 47 48 49 50 51 52 53  54  55
56 57 58 59 60 61 62 63  64  65  66
67 68 69 70 71 72 73 74  75  76  77  78
79 80 81 82 83 84 85 86  87  88  89  90  91
92 93 94 95 96 97 98 99 100 101 102 103 104 105