OFFSET
1,2
COMMENTS
The corresponding primes are A088550. - Bernard Schott, Dec 20 2012
k = 5978493 * 2^150006 - 1 is an example of a very large term of this sequence. The generated prime is proved by the N-1 method (because k is prime and k*(k+1) is fully factored and this provides for an exactly 33.33...% factorization for Phi_7(k) - 1). - Serge Batalov, Mar 13 2015
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
2 is in the sequence because 2^6 + 2^5 + 2^4 + 2^3 + 2^2 + 2 + 1 = 127, which is prime.
MAPLE
A100330 := proc(n)
option remember;
local a;
if n = 1 then
1;
else
for a from procname(n-1)+1 do
if isprime(numtheory[cyclotomic](7, a)) then
return a;
end if;
end do:
end if;
end proc:
seq(A100330(n), n=1..30) ; # R. J. Mathar, Feb 07 2014
MATHEMATICA
Select[Range[350], PrimeQ[Sum[ #^i, {i, 0, 6}]] &] (* Ray Chandler, Nov 17 2004 *)
Do[If[PrimeQ[n^6 + n^5 + n^4 + n^3 + n^2 + n + 1], Print[n]], {n, 1, 500}] (* Vincenzo Librandi, Feb 08 2014 *)
PROG
(Magma) [n: n in [1..500]| IsPrime(n^6 + n^5 + n^4 + n^3 + n^2 + n + 1)]; // Vincenzo Librandi, Feb 08 2014
(PARI) is(n)=isprime(polcyclo(7, n)) \\ Charles R Greathouse IV, Apr 28 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Ray G. Opao, Nov 16 2004
STATUS
approved