OFFSET
1,2
COMMENTS
The asymptotic density of this sequence is (3/2)*A065474 = 0.4839511484... (Erdős and Ivić, 1987). - Amiram Eldar, Feb 17 2021
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Paul Erdős and Aleksandar Ivić, The distribution of values of a certain class of arithmetic functions at consecutive integers, Colloq. Math. Soc. János Bolyai, Vol. 51 (1987), pp. 45-91.
FORMULA
a(n) = (A117205(n) + 1)/2.
EXAMPLE
10 and 2*10 - 1 = 19 are both squarefree, so 10 is in the sequence.
MAPLE
with(numtheory): a:=proc(n) if abs(mobius(n))>0 and abs(mobius(2*n-1))>0 then n else fi end: seq(a(n), n=1..160); # Emeric Deutsch, Mar 08 2006
MATHEMATICA
Select[Range[200], And@@SquareFreeQ/@{#, 2#-1}&] (* Harvey P. Dale, Dec 17 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 02 2006
EXTENSIONS
More terms from Emeric Deutsch, Mar 08 2006
STATUS
approved