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A164297
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Let S(n) be the set of all positive integers that are <= n and are coprime to n. a(n) = the number of members of S(n) that are each non-coprime with at least one other member of S(n).
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2
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0, 0, 0, 0, 2, 0, 4, 0, 3, 2, 8, 0, 9, 2, 5, 4, 13, 0, 14, 2, 7, 6, 18, 0, 15, 7, 14, 6, 24, 0, 25, 8, 14, 10, 19, 4, 31, 11, 19, 9, 35, 2, 36, 11, 17, 14, 40, 4, 35, 10, 25, 15, 45, 5, 32, 14, 28, 20, 51, 2, 52, 20, 28, 21, 40, 7, 58, 20, 35, 13, 61, 9, 62, 24, 30, 23, 50, 8, 68, 18, 43, 27
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OFFSET
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1,5
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COMMENTS
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LINKS
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EXAMPLE
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The positive integers that are <= 9 and are coprime to 9 are: 1,2,4,5, 7,8. 1 is coprime to each other member in S(9). While 2, 4, and 8 are non-coprime to each other. 5 is coprime to each other member of S(9). And 7 is also coprime to each other member. Since there are 3 integers in S(9) that are each non-coprime with at least one other member of S(9) -- these integers being 2, 4, and 8 -- then a(9) = 3.
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PROG
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(Haskell)
import Data.List ((\\))
a164297 n = length [m | let ts = a038566_row n, m <- ts,
any ((> 1) . gcd m) (ts \\ [m])]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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