|
|
A265675
|
|
Number of smaller squarefree numbers that are coprime to the n-th squarefree number.
|
|
4
|
|
|
0, 1, 2, 3, 2, 5, 3, 7, 8, 5, 6, 11, 12, 8, 9, 15, 10, 17, 8, 19, 13, 13, 15, 23, 15, 17, 26, 11, 28, 18, 30, 21, 32, 25, 23, 23, 36, 37, 25, 30, 18, 41, 29, 22, 44, 45, 30, 36, 22, 49, 32, 51, 41, 34, 39, 55, 44, 41, 38, 47, 60, 61, 30, 63, 36, 43, 66, 67
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
-> a(7) = #{1,3,7} = 3;
-> a(8) = #{1,2,3,5,6,7,10} = 7;
-> a(9) = #{1,2,3,5,6,7,10,11} = 8;
A005117(10) = 14, A005117(1..9) = [1,2,3,5,6,7,10,11,13],
-> a(10) = #{1,3,5,11,13} = 5;
A005117(11) = 15, A005117(1..10) = [1,2,3,5,6,7,10,11,13,14],
-> a(11) = #{1,2,7,11,13,14} = 6.
|
|
PROG
|
(Haskell)
import Data.List (inits)
a265675 n = a265675_list !! (n-1)
a265675_list = map (\(x:xs) -> length $ filter ((== 1) . gcd x) xs) $
map reverse $ tail $ inits a005117_list
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|