OFFSET
1,1
COMMENTS
From Amiram Eldar, Nov 02 2020: (Start)
Numbers k such that A280292(k) = 2.
The asymptotic density of this sequence is 1/Pi^2 (A092742). (End)
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
EXAMPLE
84=2*2*3*7=2*(2*3*7)=2*rad(84), therefore 84 is a term.
MATHEMATICA
4 * Select[Range[1, 100, 2], SquareFreeQ] (* Amiram Eldar, Nov 02 2020 *)
PROG
(PARI) is(n)=n%8==4 && issquarefree(n/4) \\ Charles R Greathouse IV, Jul 09 2013
(Haskell)
a081770 n = a081770_list !! (n-1)
a081770_list = filter ((== 1) . a008966 . (`div` 4)) a017113_list
-- Reinhard Zumkeller, Jul 13 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, Apr 10 2003
STATUS
approved