int main(void) {
int N;
input(&N);
bool candidates[N];
fillTrue(candidates, N);
sieveEratosthenes(candidates, N);
print(candidates, N);
return 0;
}
int main() {
int n = 500000000; // it turns out this upper limit can be a lot smaller
bool *primes = sieveEratosthenes(n);
int i = 3;
while (true) {
while (primes[i]) i += 2; // get next odd composite number
if(!isSumOfPrimeAndTwiceASq(i, primes)) break;
i += 2;
}
std::cout << "The solution is " << i << std::endl;
return 0;
}
int main() {
int n = 1000000; int sum = 0; int count = 0;
bool *primes = sieveEratosthenes(n);
for (int i = 10; i <= n; i++) {
if (isTruncLeftToRight(i, primes) && isTruncRightToLeft(i, primes)) {
count++;
sum += i;
}
}
std::cout << "We can confirm that there are " << count << " such truncatable primes. The solution is " << sum << std::endl;
return 0;
}
int main() {
int N = 1000000;
/* create an array of all primes less than N */
bool *P = sieveEratosthenes(N);
std::vector<int> allPrimesUnderN;
for (int i = 0; i < N + 1; i++) {
if (P[i]) allPrimesUnderN.push_back(i);
} // done
int count = 0;
for (int i = 0; i < allPrimesUnderN.size(); i++) {
if (isPrimeCircular(allPrimesUnderN[i], P)) count++;
}
std::cout << "The solution is " << count << std::endl;
return 0;
}
