OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = 3*A355846(n-1), for n >= 2. - Wesley Ivan Hurt, Jul 24 2022
EXAMPLE
MATHEMATICA
Select[Range[2000], SquareFreeQ[#] && And @@ PrimeQ[2# + {-1, 1}] &] (* Amiram Eldar, Dec 19 2019 *)
PROG
(Magma) [k:k in [1..2000]|IsSquarefree(k) and IsPrime(2*k-1) and IsPrime(2*k+1)]; // Marius A. Burtea, Dec 19 2019
(PARI) isok(k) = issquarefree(k) && isprime(2*k-1) && isprime(2*k+1); \\ Michel Marcus, Jul 25 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jan 10 2002
STATUS
approved