A259252 Numbers n such that 1 + sigma(n) + sigma(n)^2 + sigma(n)^3 + sigma(n)^4 + sigma(n)^5 + sigma(n)^6 is prime.

1, 2, 5, 9, 13, 16, 24, 25, 27, 28, 30, 37, 38, 39, 46, 50, 51, 55, 57, 59, 67, 68, 71, 79, 80, 82, 88, 93, 99, 105, 108, 118, 122, 125, 127, 133, 141, 145, 148, 152, 155, 157, 161, 162, 164, 179, 189, 191, 194, 196, 215, 228, 232, 237, 242, 247, 263, 281

Offset

1,2

Links

Robert Price, Table of n, a(n) for n = 1..885

OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

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

Cf. A000203, A259251, A259253.

Sequence in context: A104862 A190686 A247986 * A114471 A060636 A050877

Adjacent sequences: A259249 A259250 A259251 * A259253 A259254 A259255

Keyword

easy,nonn

Author

Robert Price, Jun 22 2015

Status

approved