OFFSET
1,1
COMMENTS
Primes dividing k^2 + 2 at least twice are in A033200. - Charles R Greathouse IV, Oct 14 2013
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
{k: k^2 + 2 is in A013929}.
EXAMPLE
4 is in the sequence because 4^2 + 2 = 18 = 2 * 3^2, which is not squarefree.
5 is in the sequence because 5^2 + 2 = 27 = 3^3, which is not squarefree.
6 is not in the sequence because 6^2 + 2 = 38 = 2 * 19, which is squarefree.
MATHEMATICA
Select[Range[300], ! SquareFreeQ[#^2 + 2] &] (* T. D. Noe, Oct 14 2013 *)
(* The following works in Mathematica versions prior to 6.0 *) Select[Range[250], MoebiusMu[#^2 + 2] == 0 &] (* Alonso del Arte, Oct 14 2013 *)
PROG
(PARI) is(n)=!issquarefree(n^2+2) \\ Charles R Greathouse IV, Oct 14 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gerasimov Sergey, Oct 14 2013
STATUS
approved