A079536 a(n) = phi(n)*d(n) - sigma(n).

0, -1, 0, -1, 2, -4, 4, 1, 5, -2, 8, -4, 10, 0, 8, 9, 14, -3, 16, 6, 16, 4, 20, 4, 29, 6, 32, 16, 26, -8, 28, 33, 32, 10, 48, 17, 34, 12, 40, 38, 38, 0, 40, 36, 66, 16, 44, 36, 69, 27, 56, 46, 50, 24, 88, 72, 64, 22, 56, 24, 58, 24, 112, 97, 108, 16, 64, 66, 80, 48, 68, 93, 70, 30, 116, 76, 144

Offset: 1

Author

N. J. A. Sloane, Jan 23 2003

Keywords

• sign

Comments

It is known that a(n) >= 0 if n is odd

References

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

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A000005, A000203, A062355, A079535, A079537.

Programs

Magma

[EulerPhi(n)*DivisorSigma(0,n) - DivisorSigma(1,n): n in [1..80]]; // G. C. Greubel, Jan 14 2019

Mathematica

Table[EulerPhi[n]*DivisorSigma[0, n] - DivisorSigma[1, n], {n,1,80}] (* G. C. Greubel, Jan 14 2019 *)

PARI

vector(80, n, eulerphi(n)*sigma(n,0) - sigma(n,1)) \\ G. C. Greubel, Jan 14 2019

Sage

[euler_phi(n)*sigma(n, 0) - sigma(n,1) for n in (1..80)] # G. C. Greubel, Jan 14 2019