A259184 a(n) = 1 - sigma(n) + sigma(n)^2.

1, 7, 13, 43, 31, 133, 57, 211, 157, 307, 133, 757, 183, 553, 553, 931, 307, 1483, 381, 1723, 993, 1261, 553, 3541, 931, 1723, 1561, 3081, 871, 5113, 993, 3907, 2257, 2863, 2257, 8191, 1407, 3541, 3081, 8011, 1723, 9121, 1893, 6973, 6007, 5113, 2257, 15253

Offset: 1

Author

Robert Price, Jun 20 2015

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A000203 (sum of divisors of n).

Cf. A259185 (indices of primes in this sequence), A259186 (corresponding primes).

Programs

Maple

with(numtheory): A259184:=n->1-sigma(n)+sigma(n)^2: seq(A259184(n), n=1..100); # Wesley Ivan Hurt, Jul 09 2015

Mathematica

Table[1 - DivisorSigma[1, n] + DivisorSigma[1, n]^2, {n, 10000}]
Table[Cyclotomic[6, DivisorSigma[1, n]], {n, 10000}]

PARI

a(n) = polcyclo(6, sigma(n)); \\ Michel Marcus, Jun 25 2015

Formula

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

a(n) = 1 - A000203(n) + A072861(n). - Omar E. Pol, Jun 20 2015

a(n) = A002061(A000203(n)). - Michel Marcus, Jun 25 2015