A bitwin chain of length one consists of two pairs of twin primes with the property that they are related by being of the form:
 |
(1)
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The first few values of 
generating bitwin chains are 6, 30, 660, 810, 2130, 2550, 3330, ... (OEIS A066388).
In general a chain of length 
consists of 
pairs of twin primes,
 |
(2)
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Bitwin chains can also be viewed as consisting of two related Cunningham chains of the first and second kinds,
 |
(3)
|
P. Jobling (1999) found the largest known chain of length six,
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(4)
|
where 
to 6.
