OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..1000
EXAMPLE
p=69497 and p+2=69499 are twin primes, also:
p-1=69496=2^3*7*17*73
p+1=69498=2*3^5*11*13
p+3=69500=2^2*5^3*139.
MAPLE
cf:= proc(n) local F;
F:= ifactors(n)[2];
max(map(t->t[2], F))>=3
end proc:
select(t -> isprime(t) and isprime(t+2) and cf(t-1) and cf(t+1) and cf(t+3), [seq(i, i=5..10^7, 6)]); # Robert Israel, Nov 24 2020
MATHEMATICA
f[m_]:=Max[Last/@FactorInteger[m]]>=3;
S={}; Do[If[PrimeQ[p=6x-1]&&PrimeQ[p+2]&&
f[p-1]==f[p+1]==f[p+3]==True, AppendTo[S, p]], {x, 1, 10^6}]; S
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jul 19 2009
EXTENSIONS
Definition clarified by Robert Israel, Nov 24 2020
STATUS
approved