A258775 -id:A258775 - cp's OEIS frontend

A258776 Primes in A258774.

3, 13, 43, 157, 73, 241, 157, 211, 601, 601, 421, 601, 2971, 1483, 8191, 6163, 3307, 2971, 6481, 8191, 28393, 3907, 28393, 6481, 8191, 28393, 37057, 26407, 12211, 28393, 31153, 113233, 19183, 83233, 113233, 37057, 28393, 71023, 22651, 83233, 37057, 154057

Offset: 1

Robert Price, Jun 09 2015

nonn

These primes are neither sorted nor uniqued. They are listed in the order found in A258774.

Robert Price, Table of n, a(n) for n = 1..2122
OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

Cf. A000203, A258774, A258775.

[a: n in [1..300] | IsPrime(a) where a is 1+SumOfDivisors(n)+ SumOfDivisors(n)^2]; // Vincenzo Librandi, Jun 10 2015

Select[Table[1 + DivisorSigma[1, n] + DivisorSigma[1, n]^2, {n, 1, 10000}], PrimeQ]
Select[Table[Cyclotomic[3, DivisorSigma[1, n]], {n, 1, 10000}], PrimeQ]

a(n) = A258774(A258775(n)).

A258774 a(n) = 1 + sigma(n) + sigma(n)^2.

Original entry on oeis.org

3, 13, 21, 57, 43, 157, 73, 241, 183, 343, 157, 813, 211, 601, 601, 993, 343, 1561, 421, 1807, 1057, 1333, 601, 3661, 993, 1807, 1641, 3193, 931, 5257, 1057, 4033, 2353, 2971, 2353, 8373, 1483, 3661, 3193, 8191, 1807, 9313, 1981, 7141, 6163, 5257, 2353

Offset: 1

Robert Price, Jun 09 2015

Robert Price, Table of n, a(n) for n = 1..10000
OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

Cf. A000203 (sum of divisors of n).

Cf. A258775 (indices of primes in this sequence), A258776 (corresponding primes).

[1+SumOfDivisors(n)+ SumOfDivisors(n)^2: n in [1..50]]; // Vincenzo Librandi, Jun 10 2015

with(numtheory): A258774:=n->1+sigma(n)+sigma(n)^2: seq(A258774(n), n=1..100); # Wesley Ivan Hurt, Jul 09 2015

Table[1 + DivisorSigma[1, n] + DivisorSigma[1, n]^2, {n, 10000}]
Table[Cyclotomic[3, DivisorSigma[1, n]], {n, 10000}]

a(n)=my(s=sigma(n)); s^2+s+1 \\ Charles R Greathouse IV, Jun 10 2015

from sympy import divisor_sigma
def A258774(n):
    return (lambda x: x*(x+1)+1)(divisor_sigma(n)) # Chai Wah Wu, Jun 10 2015

a(n) = 1 + A000203(n) + A000203(n)^2.

a(n) = 1 + A000203(n) + A072861(n). - Omar E. Pol, Jun 19 2015

cp's OEIS Frontend

A258776 Primes in A258774.

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