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A059766 Initial (unsafe) primes of Cunningham chains of first type with length exactly 6. 6
89, 63419, 127139, 405269, 810809, 1069199, 1178609, 1333889, 1598699, 1806089, 1958249, 2245319, 2606069, 2848949, 3241289, 3339989, 3784199, 3962039, 4088879, 4328459, 4444829, 4658939, 4664249, 4894889, 4897709 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Special terms of A059453. Not identical to A023330 of which 1122659,2164229,2329469,.. etc. are omitted since have exact length 7 or larger. Unsafe primes starting complete chains of length 6.

LINKS

Table of n, a(n) for n=1..25.

Chris Caldwell's Prime Glossary, Cunningham chains.

EXAMPLE

89 is here because (89-1)/2=44 and 64*89+127=5759=13.143 are composites, while 89,179,359,719,1439,2879 are primes. 1122659 is not here because initiates a chain of length 7.

CROSSREFS

Cf. A023272, A023302, A023330, A005384, A005385, A059452-A059455, A007700, A059759, A059760, A059761, A059762, A059763, A059764, A059765, A038397, A104349, A091314, A069362, A016093, A014937, A057326.

Cf. A005602, A053176, A059500, A057331, A059688, A059690.

Sequence in context: A181681 A167398 A023330 * A033513 A128872 A263379

Adjacent sequences:  A059763 A059764 A059765 * A059767 A059768 A059769

KEYWORD

nonn

AUTHOR

Labos Elemer, Feb 21 2001

EXTENSIONS

Entry revised by N. J. A. Sloane Apr 01 2006

STATUS

approved

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Last modified October 25 01:18 EDT 2020. Contains 338010 sequences. (Running on oeis4.)