OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
MAPLE
isA086708 := proc(n)
if isprime(n) then
isA046099(n-1) and isA046099(n+1) ;
else
false;
end if;
end proc:
n := 1:
for c from 1 to 50000 do
if isA086708(c) then
printf("%d %d\n", n, c) ;
n := n+1 ;
end if;
end do: # R. J. Mathar, Dec 08 2015
Res:= NULL: count:= 0:
p:= 1:
while count < 100 do
p:= nextprime(p);
if max(seq(t[2], t=ifactors(p-1)[2]))>=3 and max(seq(t[2], t=ifactors(p+1)[2]))>=3 then
count:= count+1; Res:= Res, p;
fi
od:
Res; # Robert Israel, Jul 11 2018
MATHEMATICA
f[n_]:=Max[Last/@FactorInteger[n]]; lst={}; Do[p=Prime[n]; If[f[p-1]>=3&&f[p+1]>=3, AppendTo[lst, p]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 03 2009 *)
dbcQ[p_]:=AnyTrue[Surd[#, 3]&/@Rest[Divisors[p-1]], IntegerQ]&&AnyTrue[Surd[#, 3]&/@Rest[ Divisors[ p+1]], IntegerQ]; Select[ Prime[Range[1500]], dbcQ] (* Harvey P. Dale, Sep 21 2024 *)
PROG
(PARI)
\\ Input no. of iterations n, power p and number to subtract and add k.
powerfreep4(n, p, k) = { c=0; pc=0; forprime(x=2, n, pc++; if(!ispowerfree(x-k, p) && !ispowerfree(x+k, p), c++; print1(x", "); ) ); print(); print(c", "pc", "c/pc+.0) }
ispowerfree(m, p1) = { flag=1; y=component(factor(m), 2); for(i=1, length(y), if(y[i] >= p1, flag=0; break); ); return(flag) } \\ Cino Hilliard, Dec 08 2003
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls and Amarnath Murthy, Jul 28 2003
EXTENSIONS
Definition clarified by Harvey P. Dale, Sep 21 2024
STATUS
approved