OFFSET
1,1
COMMENTS
Numbers k such that k is squarefree, k-1 and k+1 are primes.
All terms are multiples of 6. - Zak Seidov, Mar 20 2016
All terms == 6 (mod 12). - Robert Israel, Mar 21 2016
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
select(t -> numtheory:-issqrfree(t) and isprime(t+1) and isprime(t-1),
[seq(i, i=6..10000, 12)]); # Robert Israel, Mar 21 2016
MATHEMATICA
Select[12 * Range[0, 500] + 6, PrimeQ[#-1] && PrimeQ[#+1] && SquareFreeQ[#] &] (* Amiram Eldar, May 23 2022 *)
PROG
(PARI) {forstep(n=6, 8000, 12, if(issquarefree(n)&&isprime(n-1)&&isprime(n+1), print1(n", "))); } \\ Zak Seidov, Mar 20 2016
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre and Labos Elemer, May 06 2002
STATUS
approved