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• ## Re: [PrimeNumbers] Extension of Cunningham chains

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• ... Add to that a 4-divisor Cunningham chain (of the first kind) of length 18: 899643225*2^8+1 == 173 * 1331263963 899643225*2^9+1 == 2347 * 196257917
Nov 13, 2004 1 of 6
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I previously wrote:
> So far, I've found a "4-divisor Cunningham chain" (of the second kind)
> of length 18...

Add to that a "4-divisor Cunningham chain" (of the first kind) of length 18:

899643225*2^8+1 == 173 * 1331263963
899643225*2^9+1 == 2347 * 196257917
899643225*2^10+1 == 53 * 17381786083
899643225*2^11+1 == 397 * 4640980667
899643225*2^12+1 == 821 * 4488354019
899643225*2^13+1 == 2351 * 3134784049
899643225*2^14+1 == 1531 * 9627534029
899643225*2^15+1 == 19 * 1551553115621
899643225*2^16+1 == 71 * 830408709769
899643225*2^17+1 == 11 * 10719821526109
899643225*2^18+1 == 193 * 1221948567743
899643225*2^19+1 == 101 * 4670021258899
899643225*2^20+1 == 532663 * 1770996473
899643225*2^21+1 == 499 * 3780939055301
899643225*2^22+1 == 9008023 * 418890713
899643225*2^23+1 == 19427 * 388467306037
899643225*2^24+1 == 122953 * 122758360583
899643225*2^25+1 == 5205467 * 5799098797

So I've got two examples of length 18, a "4DCC1K" and a "4DCC2K". :)

The challenge is this: find a chain of length 19, any number
of divisors you wish. :)
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