Increasing Number Triangle Starting from 11 in Python

What You’ll Learn

The increasing number triangle from 11 prints 11, 12 13, 13 14 15, … — a natural step after the number-star diamond in Program 31. This tutorial covers the 9 + i + j formula, nested loops, a live preview, worked Python examples, edge cases, and complexity.

📝 Problem & Approach

Given rows = 5, print a left-shifted increasing triangle: for each row i, print j = 1..i values of 9 + i + j separated by spaces.

# rows = 5 (conceptual shape)
for i in range(1, rows + 1):
    for j in range(1, i + 1):
        print(9 + i + j, end=" ")
    print()

Inputs & Outputs

Minimal workflow

for i from 1 to rows:
    for j from 1 to i:
        print (9 + i + j) + space
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 3 and 9 and draw the increasing triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete Python programs — fixed rows, custom base input, and a smaller trace demo. Click View Output to reveal sample console results.

for i in range(1, 6):
    for j in range(1, i + 1):
        print(9 + i + j, end=" ")
    print()

11
12 13
13 14 15
14 15 16 17
15 16 17 18 19

rows = int(input("Enter rows: "))
baseVal = int(input("Enter base: "))
if rows < 1:
    raise SystemExit

for i in range(1, rows + 1):
    for j in range(1, i + 1):
        print(baseVal + i + j, end=" ")
    print()

Enter rows: 3
Enter base: 9
11
12 13
13 14 15

rows = 3

for i in range(1, rows + 1):
    for j in range(1, i + 1):
        print(9 + i + j, end=" ")
    print()

11
12 13
13 14 15

🔎 Worked Walkthrough — rows = 5

Trace each outer-loop value of i, inner-loop range, values printed, and full row output.

Prints per row = i — total prints = n(n+1)/2 for n rows.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices