# Euler problems/121 to 130

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## Problem 121

Investigate the game of chance involving coloured discs.

Solution:

```problem_121 = undefined
```

## Problem 122

Finding the most efficient exponentiation method.

Solution:

```problem_122 = undefined
```

## Problem 123

Determining the remainder when (pn − 1)n + (pn + 1)n is divided by pn2.

Solution:

```problem_123 = undefined
```

## Problem 124

Determining the kth element of the sorted radical function.

Solution:

```problem_124 = undefined
```

## Problem 125

Finding square sums that are palindromic.

Solution:

```problem_125 = undefined
```

## Problem 126

Exploring the number of cubes required to cover every visible face on a cuboid.

Solution:

```problem_126 = undefined
```

## Problem 127

Investigating the number of abc-hits below a given limit.

Solution:

```problem_127 = undefined
```

## Problem 128

Which tiles in the hexagonal arrangement have prime differences with neighbours?

Solution:

```problem_128 = undefined
```

## Problem 129

Investigating minimal repunits that divide by n.

Solution:

```problem_129 = undefined
```

## Problem 130

Finding composite values, n, for which n−1 is divisible by the length of the smallest repunits that divide it.

Solution:

```problem_130 = undefined
```