Palindromic Merlon Primes - Program Outputs

7*(10¹¹-1)/9 - 6*10¹⁰ - 6*10⁵ - 6

Using Pari/gp (< 1s)
     gp > isprime(7*(10^11-1)/9-6*10^10-6*10^5-6)
     %1 = 1

7*(10⁴⁷-1)/9 - 6*10⁴⁶ - 6*10²³ - 6

Using Pari/gp (< 1s)
     gp > isprime(7*(10^47-1)/9-6*10^46-6*10^23-6)
     %1 = 1

7*(10⁶³⁵-1)/9 - 6*10⁶³⁴ - 6*10³¹⁷ - 6

Using Pari/gp (time = 12,063 ms)
     gp > default(parisizemax,"1G")
     gp > isprime(7*(10^635-1)/9-6*10^634-6*10^317-6)
     %1 = 1

7*(10⁸⁸⁷-1)/9 - 6*10⁸⁸⁶ - 6*10⁴⁴³ - 6

Using Pari/gp (1min, 2,672 ms)
     gp > default(parisizemax,"1G")
     gp > isprime(7*(10^887-1)/9-6*10^886-6*10^443-6)
     %1 = 1

Patrick De Geest - Belgium