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# Competition #4

This competition is organized by Макарова Наталия (Natalia Makarova)

## Definitions

### Definition 1:

A prime k-tuple is a finite collection of values (p + a1, p + a2, p + a3, …, p + ak), where p, p + a1, p + a2, p + a3, …, p + ak are prime numbers, (a1, a2, a3, …, ak) are pattern. Typically the first value in the pattern is 0 and the rest are distinct positive even numbers.

We consider the k-tuple, where p + a1, p + a2, p + a3, …, p + ak are consecutive primes.

### Definition 2:

k-tuple (p + a1, p + a2, p + a3, …, p + a [k / 2], p + a [k / 2+1], …, p + a [k-2], p + a [k-1], p + ak) for k even, is called symmetric, if the following condition is satisfied:
a1 + ak = a2 + a[k-1] = a3 + a[k-2] = … = a[k/2] + a[k/2+1]

Example: symmetric 8-tuple

`(17 + 0, 17 + 2, 17 + 6, 17 + 12, 17 + 14, 17 + 20, 17 + 24, 17 + 26)`

Shortened we write this:

`17: 0, 2, 6, 12, 14, 20, 24, 26`

### Definition 3:

k-tuple (p + a1, p + a2, p + a3, …, p + a [(k-1) / 2], p + a [(k-1) / 2 + 1], p + a [(k-1) / 2 + 2], …, p + a [k-2], p + a [k-1], p + ak) for k odd called symmetric, if the following condition is satisfied:
a1 + ak = a2 + a[k-1] = a3 +a [k-2] =…= a[(k-1)/2] + a[(k-1)/2+2] = 2 a[(k-1)/2+1]

Example: symmetric 5-tuple

`18713: 0, 6, 18, 30, 36`

### Definition 4:

The diameter d of k-tuple is the difference of its largest and smallest elements.

Example: 8-tuple

`17: 0, 2, 6, 12, 14, 20, 24, 26`

It has a diameter d = 26.

### Definition 5:

A pandiagonal magic square is a magic square with the additional property that the broken diagonals, i.e. the diagonals that wrap round at the edges of the square, also add up to the magic constant.

## The Contest

In the contest is required to compete for those tasks:

Required to find k-tuples with the minimal value p:
for an even k > 24; for odd k > 15.

Example

```15-tuple, p=3945769040698829 (minimal)
3945769040698829: 0, 12, 18, 42, 102, 138, 180, 210, 240, 282, 318, 378, 402, 408, 420```

Required to find k-tuples with a minimal diameter d:
for an even k > 10; for odd k > 13.

Example
8-tuple with a minimal diameter d = 26

`17: 0, 2, 6, 12, 14, 20, 24, 26`

Required to find the 16-tuple, the elements of which it is possible to make pandiagonal magic square of order 4 with magic constant S as: 94615738903617540 < S < 29643562211780078520 Example 16-tuple

`23653934725904299: 0, 12, 22, 34, 48, 60, 70, 82, 90, 102, 112, 124, 138, 150, 160, 172`

pandiagonal magic square

```23653934725904299+
0  160   60  124
82  102   22  138
112   48  172   12
150   34   90   70

S=94615738903617540
```

### Rule:

Prime numbers can contain no more than 100 digits.

In tasks 1 and 2 k <= 50.

## Format of solution

For every task the first line is the number of task you are entering: so 1, 2 or 3. After there are those lines according to the tasks you are inserting.

k-tuple is represented as

`p: a1, a2, a3, …, ak`

Example

`18713: 0, 6, 18, 30, 36`

it is 16-tuple and pandiagonal magic square of order 4, composed of the elements of the tuple.

Example

```23653934725904299: 0, 12, 22, 34, 48, 60, 70, 82, 90, 102, 112, 124, 138, 150, 160, 172
0, 160, 60, 124, 82, 102, 22, 138, 112, 48, 172, 12, 150, 34, 90, 70
```

## Scoring

The contestant receives one point for every solution to tasks 1 and 3.
For each k in task 2 one point counted towards only those participants, who will have a minimum diameter d.

## The Prize

If two or more contestants have equal number of points, the winner will be the entrant who submitted solutions ahead of other contestants.
The winner will receive a prize of 5,000 rubles.
If the winner is not from Russia, the prize will be paid in US dollars at the official exchange rate on the day ending of the contest.

## Thanks

We thanks  Wolfram Alpha as we use their API for testing the primality of the given big numbers.

1 vote

### 2 Responses to “Primes k-tuple”

1. Dmitriy40 ha detto:

For problem 2 sequences of length 12 with a minimum diameter is easy to generate thousands – will be given for every point? Then there is no need to look for the rest of the sequence.

2. primesmagicgames ha detto:

It will be give only one point for the entry with minimal diameter for different starting prime number.