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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
OFFSET
1,1
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
KEYWORD
nonn,fini,full
STATUS
approved