OFFSET
1,1
COMMENTS
Numbers k such that, for some prime p == 1 (mod 6), 2*k-1 is a square root of -3 (mod p^2).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3) = 31 is a term because 31^2 - 31 + 1 = 931 is divisible by 7^2.
MAPLE
remove(t -> numtheory:-issqrfree(t^2-t+1), [$1..1000]);
MATHEMATICA
Select[Range[1000], ! SquareFreeQ[#^2 - # + 1] &] (* Amiram Eldar, Feb 02 2022 *)
PROG
(PARI) isok(k) = !issquarefree(k^2 - k + 1); \\ Michel Marcus, Feb 02 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Feb 01 2022
STATUS
approved