8*(105-1)/9 - 104 - 102 - 1
Using Pari/gp (< 1s)
     gp > isprime(8*(10^5-1)/9-10^4-10^2-1)
     %1 = 1


8*(1011-1)/9 - 1010 - 105 - 1
Using Pari/gp (< 1s)
     gp > isprime(8*(10^11-1)/9-10^10-10^5-1)
     %1 = 1


8*(10257-1)/9 - 10256 - 10128 - 1
Using Pari/gp (< 1s)
     gp > default(parisizemax,"1G")
     gp > isprime(8*(10^257-1)/9-10^256-10^128-1)
     %1 = 1


8*(10661-1)/9 - 10660 - 10330 - 1
Using Pari/gp (time = 19,892 ms)
     gp > default(parisizemax,"1G")
     gp > isprime(8*(10^661-1)/9-10^660-10^330-1)
     %1 = 1


8*(101609-1)/9 - 101608 - 10804 - 1
Using Pari/gp (time = 17min, 27,828 ms)
     gp > default(parisizemax,"1G")
     gp > isprime(8*(10^1609-1)/9-10^1608-10^804-1)
     %1 = 1


8*(103683-1)/9 - 103682 - 101841 - 1
C:\pfgw>pfgw64 -q"8*(10^3683-1)/9-10^3682-10^1841-1"
PFGW Version 4.0.4.64BIT.20221214.Win_Dev [GWNUM 30.11]

8*(10^3683-1)/9-10^3682-10^1841-1 is 3-PRP! (0.0750s+0.0003s)









 

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Patrick De Geest - Belgium flag - Short Bio - Some Pictures
E-mail address : pdg@worldofnumbers.com