Hello everyone,

It has been time TI-Planet have not organized a contest, and here is the lack filled

So we organize a contest, about 5 weeks, well mixing arithmetic and algorithmics.

**Introduction:**In mathematics, a

**prime palindom number** is a number which is both prime and palindromic.

A

**prime number** is an integer that only admits two positive and integer divisors (which are 1 and itself).

This definition excludes 1, which has only one positive and integer divisor ; it excludes 0 too, which is divisible by all the positive integers.

For example 6 = 2 × 3 is not prime and 21 = 3 × 7 or 7 × 3 either. But 11 is prime because 1 and 11 are the only divisors of 11.

So, the prime numbers are, in order, 2, 3, 5, 7, 11...

A

**palindromic number** is a number whose writing (in base 10) is read in the same way from left to right and from right to left.

For example, all the 1-digit numbers are palindromic: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

The 2-digit palindroms are: 11, 22, 33, 44, 55, 66, 77, 88 and 99.

101 is a 3-digit palindromic number.

So, the

*prime palindromic numbers* are: 2, 3, 5, 7, 11, 101, 131...

**Subject :** Make a program fastest as possible to find the n-th prime palindromic number.

**Plateform : **The candidate will perform its participation:

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

**Categories:**The candidate's production will be judged in one of those categories:

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

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

For example, to obtain the 42th 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 send the result 18181 in Ans, reusable in the home screen for calculations.

On TI-Nspire, the main program should be a function which take the n parameter and which sends the result. For example, palprem(42) should answer 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.

**Notation :** 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 : **Participations are rated on an equitable 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 finishs Sunday the 12th of May, 23h59 (GMT+1)

**How ? : **To participate, candidates must send to the email address

[email protected] :

- complete mailing address with first and last name
- a valid email address for contact
- the expected production (8xp, 83p, tns)
- any other information or file deemed useful by the candidate concerning its production

The e-mail correctly send is taken as an entry.

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

- 1st price: 1 calculator + 4 TI-Planet stickers
- 2nd price: 1 poster TI + 3 TI-Planet stickers
- 3rd price: 2 TI-Planet stickers

1st price in the Nspire category: a TI-Nspire CX (not CAS)

1st price in the TI-82/83/84 category : a TI-84 Pocket.fr

**Complete rules:** The complete rules for this contest, legally registered to an usher, are available on

TI-Planet or

the UPECS website. (French)

See you soon on TI-Planet !

*PS: I know I'm a bit late, because the contest has started...*