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A070195 Squarefree numbers sandwiched between a pair of twin primes. 4
6, 30, 42, 102, 138, 282, 462, 570, 618, 642, 822, 858, 1230, 1290, 1302, 1482, 1698, 1722, 1878, 2082, 2130, 2238, 2310, 2382, 2658, 2730, 2802, 3390, 3462, 3558, 3918, 3930, 4002, 4218, 4242, 4422, 4638, 4722, 5010, 5442, 5478, 5502, 5658, 6090, 6198 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Numbers k such that k is squarefree, k-1 and k+1 are primes.
Intersection of A005117 and A014574. - Michel Marcus, Mar 06 2014
Also, intersection of A077064 and A077067. - Zak Seidov, Mar 20 2016
All terms are multiples of 6. - Zak Seidov, Mar 20 2016
All terms == 6 (mod 12). - Robert Israel, Mar 21 2016
LINKS
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
Cf. A005117, A014574, A077064, A077067. - Zak Seidov, Mar 20 2016
Sequence in context: A090126 A291566 A326580 * A241190 A276933 A110175
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre and Labos Elemer, May 06 2002
STATUS
approved

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Last modified February 28 08:45 EST 2024. Contains 370393 sequences. (Running on oeis4.)