OFFSET
1,2
LINKS
Robert Price, Table of n, a(n) for n = 1..885
MAPLE
with(numtheory): A259252:=n->`if`(isprime(1 + sigma(n) + sigma(n)^2 + sigma(n)^3 + sigma(n)^4 + sigma(n)^5 + sigma(n)^6), n, NULL): seq(A259252(n), n=1..500); # Wesley Ivan Hurt, Jul 09 2015
MATHEMATICA
Select[Range[10000], PrimeQ[ 1 + DivisorSigma[1, #] + DivisorSigma[1, #]^2 + DivisorSigma[1, #]^3 + DivisorSigma[1, #]^4 + DivisorSigma[1, #]^5 + DivisorSigma[1, #]^6] &]
Select[Range[10000], PrimeQ[ Cyclotomic[7, DivisorSigma[1, #]]] &]
PROG
(PARI) isok(n) = isprime(polcyclo(7, sigma(n))); \\ Michel Marcus, Jun 23 2015
(Magma) [n: n in [1..500] | IsPrime(1 + DivisorSigma(1, n) + DivisorSigma(1, n)^2 + DivisorSigma(1, n)^3 + DivisorSigma(1, n)^4 + DivisorSigma(1, n)^5+ DivisorSigma(1, n)^6)]; // Vincenzo Librandi, Jun 24 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Robert Price, Jun 22 2015
STATUS
approved