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A164296
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 coprime to every other member of S(n).
2
1, 1, 2, 2, 2, 2, 2, 4, 3, 2, 2, 4, 3, 4, 3, 4, 3, 6, 4, 6, 5, 4, 4, 8, 5, 5, 4, 6, 4, 8, 5, 8, 6, 6, 5, 8, 5, 7, 5, 7, 5, 10, 6, 9, 7, 8, 6, 12, 7, 10, 7, 9, 7, 13, 8, 10, 8, 8, 7, 14, 8, 10, 8, 11, 8, 13, 8, 12, 9, 11, 9, 15, 10, 12, 10, 13, 10, 16, 10, 14, 11, 13, 10, 18, 11, 14, 10, 14, 10, 20
OFFSET
1,3
COMMENTS
A164296(n) + A164297(n) = phi(n) (= A000010(n) = the number of elements in S(n)).
LINKS
EXAMPLE
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 coprime to each other member -- these integers being 1, 5, and 7 -- then a(9) = 3.
PROG
(Haskell)
import Data.List ((\\))
a164296 n = length [m | let ts = a038566_row n, m <- ts,
all ((== 1) . gcd m) (ts \\ [m])]
-- Reinhard Zumkeller, May 28 2015
CROSSREFS
Cf. A164297.
Sequence in context: A066691 A260123 A319411 * A319817 A233566 A319818
KEYWORD
nonn
AUTHOR
Leroy Quet, Aug 12 2009
EXTENSIONS
Extended by Ray Chandler, Mar 16 2010
STATUS
approved