Pseudocode using a repeat-until loop to output the first five square numbers.

Thank you.

n = 1

10 output = n*n
print output

n = n+1

if n = 6 quit

otherwise go back up to 10

n=1

s=1
for (i=1;i<=5;i++) {
print s;
n += 2;
s += n
}

To generate the first five square numbers using a repeat-until loop, you can follow these steps in pseudocode:

1. Set a variable, "count," to 1 to keep track of the number of squares generated.
2. Set a variable, "number," to 1 to start generating squares from 1.
3. Begin the repeat-until loop:

a. Output the square of the current number, i.e., "number * number."
b. Increment the count by 1.
c. Increment the number by 1.
d. Repeat until the count reaches 5.

Here's the pseudocode representation:

```
count = 1
number = 1

repeat until count = 6:
square = number * number
output square
count = count + 1
number = number + 1
```

In this pseudocode, the repeat-until loop will iterate until the "count" variable reaches 6 (after outputting the fifth square number). During each iteration, the loop calculates the square of the "number" variable, outputs the result, increments the count, and increments the number.