Question

VIEIJ. Put 444 KB) Page 1 of 3 20. A safe prime is a prime number that can be written in the form 2p +1 wherep is also a prime number. For example, 47 is a safe prime since 47 =2x23 +1 and 23 is also a prime number. Write a computer program that finds and displays all the safe primes between 1 and 1,000. Do not use MATLABs built-in function isprime. A BU DO WAY Ox) v Pg Me O EDIT

Answer 1

%matlab code
function is_prime = checkPrime(n)
if (n <= 1)
is_prime = false;
return
elseif (n <= 3)
is_prime = true;
return
end
  
if (mod(n,2) == 0 || mod(n,3) == 0)
is_prime = false;
return
end

i = 5;
while i*i <= n
if (mod(n,i) == 0 || mod(n,(i+2)) == 0)
is_prime = false;
return
end
i = i+6;
end
is_prime = true;
end

% find safe prime
a = 1;
b = 1000;
for i = a:b
if (checkPrime(i) && (mod(i, 2) == 1) && checkPrime((i-1)/2))
fprintf("%d ", i)
end
end
fprintf("\n")

Sample output:

5 7 11 23 47 59 83 107 167 179 227 263 347 359 383 467 479 503 563 587 719 839 863 887 983