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A020607 Smallest nonempty set S containing prime divisors of 7k + 1 for each k in S. 0
2, 3, 5, 11, 13, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

7 * 2 + 1 = 15 = 3 * 5, both of which are in the set.

7 * 3 + 1 = 22 = 2 * 11, both of which are in the set.

7 * 5 + 1 = 36 = 2^2 * 3^2; both 2 and 3 are in the set.

7 * 11 + 1 = 78 = 2 * 3 * 11, all three of which are in the set.

7 * 13 + 1 = 92 = 2^2 * 23; both 2 and 23 are in the set.

7 * 23 + 1 = 162 = 2 * 3^4; both 2 and 3 are in the set.

CROSSREFS

Cf. A020575, A020581, A020587, A020602.

Sequence in context: A053184 A228445 A287164 * A235631 A180640 A128425

Adjacent sequences:  A020604 A020605 A020606 * A020608 A020609 A020610

KEYWORD

nonn,fini,full

AUTHOR

David W. Wilson

STATUS

approved

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Last modified July 6 14:10 EDT 2022. Contains 355110 sequences. (Running on oeis4.)