Start with option -Xmx12G or more(needs lots of ram). Other possibillity is to set maxPrimeNumber in Config.java to a smaller value.
At the first run a prime database gets generated with all prime numbers from variables 0 to maxPrimeNumber= from Config.java. After that, prime chains will get searched betwen the variables startChainSearch and stopChainSearch from Config.java. All further runs will use the prime database file and will be faster. If you change maxPrimeNumber= from Config.java delete the prime database first so the primes get regenerated.
Longest primechain from 0 to INT32_MAX is [31, 331, 3331, 33331, 333331, 3333331, 33333331].
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