TI-Planet has announced a short, simple contest and I thought others here would be interested. For those not familiar, TI-Planet is a French site and they often cross-post news with Omnimaga and likewise, they open up their competitions to the other communities. Anyway, the subject of this competition:

**Prime Palindromes**

What is a palindrome?

A palindrome is a sequence of characters or digits that can be read the same backwards or forwards. Examples include 11,1111,12435253421.

What is a prime?

A prime number is a positive integer ({1,2,3,4,…}) that is only divisible by 1 and itself. 1 is neither prime nor composite. The first few primes are 2,3,5,7,11,13,17,19. Some non-primes are 6 (6=2x3), 55 (55=5*11), 111 (111=3*37).

What is a prime palindrome?

Combine the two properties above, and you have a prime palindrome. The first few are 2,3,5,7,11,101,131.

**Subject**

Make a program to find the n^{th} prime palindrome as fast as possible.

**Platforms**

The following calculators are allowed:

- TI-Nspire
- TI-82Stats/83/76
- TI-83+/84

**Categories**

The following categories will be used for judging:

- TI-Nspire
- TI-82Stats/83/84/76
- I think this gets further split up into Assembly and BASIC

**Languages**

- TI-Basic Nspire
- TI-Basic TI-82Stats/83/84/76
- TI-83+/84 Assembly NO SHELL (So, you can participate with Axe compiled for no shell)
- TI-82Stats/83/76 Assembly NO SHELL

NB: on TI-82Stats/83/84,TI-Basic and assembly combinations are allowed

**Constraints**

On the TI-82Stats/83/84/76, the program will catch n in the 'Ans' variable, and will return the nth prime palindromic number as a result in Ans.

For example, to obtain the 42nd prime, we will type:

- TI-Basic program: 42:prgmPALPREM
- TI-83+/84 Assembly program: 42:Asm(prgmPALPREM
- TI-82Stats/83/76 Assembly program: 42:Send(9prgmPALPREM

In each case, the program should return the result 18181 in Ans, reusable in the home screen for calculations.

On the TI-Nspire, the main program should be a function which takes the n parameter and returns the result. For example, palprem(42) should return 18181.

YOU MUST NOT USE a pre-calculated list of prime palindromic numbers in your program, directly under penalty of disqualification.

YOU MUST NOT USE functions like isPrime() which would provide a direct response. It destroys the value of algorithmic thinking, and it would be unfair to those who don't have this function…

The program MUST run on not-CAS TI-Nspires.

**Score**

The final score will be on 20 points, and the scale is as follows:

- 3 points for the proper functioning of the program
- 10 points for the fast execution of the program (it will be tested and compared to competitors on identical machines with identical languages)
- 3 points for the respect of the rules
- 4 points for an explanation

**Jury**

Entries are rated on an equal basis according to a common scale by a jury whose composition is as follows:

- Adriweb
- Critor
- Laurae
- Levak
- Lionel Debroux

**When**

The contest starts Monday the 1st of April 2013 and finishes Sunday the 12th of May, 23h59 (GMT+1)

**Submissions**

To participate, candidates must send to the email address gro.tenalpit|ofni#gro.tenalpit|ofni :

complete mailing address with first and last name

- a valid email address for contact
- the program entry (8xp, 83p, tns)
- any other information or file deemed useful by the candidate concerning its production (such as a readme)

Correctly sent emails are taken as an entries.

**Lots**

Through our partnership with TI-France and Jarrety, the winners of the contest (one winner per category) will be rewarded with:

- 1st prize: 1 calculator + 4 TI-Planet stickers
- 2nd prize: 1 poster TI + 3 TI-Planet stickers
- 3rd prize: 2 TI-Planet stickers
- 1st prize in the Nspire category: a TI-Nspire CX (not CAS)
- 1st prize in the TI-82/83/84 category : a TI-84 Pocket.fr

**Complete Rules**

These are in French, but the complete, formal rules can be located at TI-Planet or the UPECS website.

Z80 Assembly>English>TI-BASIC>Python>French>C>0