A079538 a(n) = sigma[k](n) - phi(n)^k - d(n)^k for k=2.

-1, 0, 2, 8, 6, 30, 10, 53, 46, 98, 18, 158, 22, 198, 180, 252, 30, 383, 34, 446, 340, 494, 42, 722, 242, 690, 480, 870, 54, 1172, 58, 1073, 804, 1178, 708, 1686, 70, 1470, 1108, 1890, 78, 2292, 82, 2126, 1754, 2150, 90, 3054, 678, 2819, 1860, 2958, 102, 3712, 1556, 3610

Offset

1,3

Comments

It is known that a(n) >= 0 for n >= 2.

References

D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 10.

Links

T. D. Noe, Table of n, a(n) for n=1..10000

Formula

a(n) = 2*n - 4 for prime n. - T. D. Noe, Dec 19 2006

Mathematica

Table[DivisorSigma[2, n] - EulerPhi[n]^2 - DivisorSigma[0, n]^2, {n, 80}] (* G. C. Greubel, Jan 15 2019 *)

Prog

(PARI) vector(80, n, sigma(n, 2) - eulerphi(n)^2 - numdiv(n)^2) \\ G. C. Greubel, Jan 15 2019
(Magma) [DivisorSigma(2, n) - EulerPhi(n)^2 - DivisorSigma(0, n)^2: n in [1..80]]; // G. C. Greubel, Jan 15 2019
(Sage) [sigma(n, 2) - euler_phi(n)^2 - sigma(n, 0)^2 for n in (1..80)] # G. C. Greubel, Jan 15 2019

Crossrefs

Cf. A000010, A000005, A000203, A046520 (for k=1), A079539.

Sequence in context: A069895 A370925 A085590 * A098221 A343101 A334519

Adjacent sequences: A079535 A079536 A079537 * A079539 A079540 A079541

Keyword

sign

Author

N. J. A. Sloane, Jan 23 2003

Status

approved