static bool IsPrimeProof(mpz_t n)
{
var ns = n.ToString();
var digits = ns.ToCharArray();
char[] digitsCopy = new char[digits.Length];
for (int di = 0; di < digits.Length; di++)
{
int digit = digits[di];
var low = di == 0 ? '1' : '0';
for (char odigit = low; odigit <= '9'; odigit++)
{
if (odigit != digit)
{
Array.Copy(digits, digitsCopy, digits.Length);
digitsCopy[di] = odigit;
var cand = new mpz_t(new string(digitsCopy));
if (cand.IsProbablyPrimeRabinMiller(10))
{
return(false);
}
}
}
}
return(true);
}
static int NumPrimes(int a, int b)
{
for (int n = 0; ; n++)
{
mpz_t bign = new mpz_t(n);
mpz_t p = bign.Power(2) + bign.Multiply(a) + b;
if (!p.IsProbablyPrimeRabinMiller(10))
{
return(n);
}
}
}
static bool IsCircular(mpz_t p)
{
string ps = p.ToString();
if (ps.Length > 1 && telltaleChars.IsMatch(ps))
{
return(false);
}
for (int i = 1; i < ps.Length; i++)
{
string c = $"{ps.Substring(i)}{ps.Substring(0, i)}";
var pr = new mpz_t(c);
if (!pr.IsProbablyPrimeRabinMiller(10))
{
return(false);
}
}
return(true);
}
static bool IsTruncatable(mpz_t p)
{
if (p <= 7)
{
return(false);
}
var ps = p.ToString();
foreach (var truncate in truncates)
{
for (string pstrunc = truncate.Replace(ps, string.Empty);
pstrunc.Length > 0;
pstrunc = truncate.Replace(pstrunc, string.Empty))
{
var ptrunc = new mpz_t(pstrunc);
if (!ptrunc.IsProbablyPrimeRabinMiller(10))
{
return(false);
}
}
}
return(true);
}
