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 2017-09-27, 01:28 #1 Citrix     Jun 2003 1,579 Posts Super Cullen & Woodall primes Super Cullen and Woodall defined as:- C(n)= n*2^(n*n)+1 W(n)= n*2^(n*n)-1 Primes so far 1*2^1-1 1*2^1+1 2*2^4-1 5*2^25+1 9*2^81+1 I think there are finite number of these primes, but I still wanted to search further. I have checked these up to 5 Million bits and plan to search further. I am using srsieve to sieve these numbers. Is there a faster sieve software or can gcwsieve be made faster for these numbers?
 2017-10-26, 09:12 #2 Citrix     Jun 2003 1,579 Posts I have completed this to 8M bits. Continuing. I am using the following code to sieve. Does anyone have any suggestions on how to make this faster? Thanks. Code: //Adapted from multisieve void SuperCullenWoodallSieve::DoWork64Bit(uint64_t thePrime) { uint32_t nmin, nmax; nmin = 100; nmax = 32768; uint64_t temp, power; temp = thePrime + 1; temp >> 1; temp = expmod62(temp, nmax*nmax, thePrime); power = expmod62(2, 2 * nmax, thePrime); for (int x = nmax; x >= nmin; x--) { if (temp == x) LogFactor('-', x, 2, thePrime); if (temp == thePrime - x) LogFactor('+', x, 2, thePrime); temp = mulmod62(temp, power, thePrime); if (temp&1) { temp = temp + thePrime; } temp >> 1; if (power&1) { power = power + thePrime; } power >> 1; if (power&1) { power = power + thePrime; } power >> 1; } }

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