Monday, April 29, 2019

mathematics - Prime to Prime: Get all first 25 Prime Numbers using up to 4 Primes



The first 25 Prime Numbers are



2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97



Using up to 4 prime numbers and the following mathematical operations, get all the 25 primes.



+ - x / ^ √ !



No other operators (like !!) are allowed.


Other rules




  • You cannot use same Prime Number more than once.

  • You can use only Prime Numbers.

  • Any number that appears as a number in the equation will be counted as one of the primes out of four (e.g. 7^2 means you have used both 7 and 2).

  • You do not have to use all the 4 primes in every equation.

  • You must use the SAME 4 primes in every equation. If you select say 2, 13, 17, 23 then they are the only primes that to appear in every equation to get the 25 primes.


I have 1 solution. There may be more.


No programming please.
NO PARTIAL ANSWERS.




Answer



Using 2,3,7,11:



$2 = 2$


$3 = 3$


$5 = 11 + 3 - 7 -2$


$7 = 7$


$11 = 11$


$13 = 2 + 11$


$17 = 3! + 11$



$19 = 2^3 + 11$


$23 = 3 \cdot 7 + 2$


$29 = \frac{(7-2)!}{3} - 11$


$31 = 3 \cdot 11- 2$


$37 = (11-3!) \cdot 7 + 2$


$41 = 7^2 +3 - 11$


$43 = 2 \cdot 11 + 3 \cdot 7$


$47 = 3 \cdot 11 + 2 \cdot 7$


$53 = 2^ {3!} - 11$


$59 = 3! \cdot 11 - 7$



$61 = (11-2) \cdot 3! + 7$


$67 = 7 \cdot 2^3 + 11$


$71 = 2^{3!} + 7$


$73 = 3! \cdot 11 + 7$


$79 = 7 \cdot 11 + 2$


$83 = 7 \cdot 11 + 3!$


$89 = 7 \cdot 11 + 2 \cdot 3!$


$97 = (2+11) \cdot 7 + 3!$



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