OFFSET
1,5
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
MATHEMATICA
Table[EulerPhi[n]*DivisorSigma[0, n] - DivisorSigma[1, n], {n, 1, 80}] (* G. C. Greubel, Jan 14 2019 *)
PROG
(PARI) vector(80, n, eulerphi(n)*sigma(n, 0) - sigma(n, 1)) \\ G. C. Greubel, Jan 14 2019
(Magma) [EulerPhi(n)*DivisorSigma(0, n) - DivisorSigma(1, n): n in [1..80]]; // 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
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Jan 23 2003
STATUS
approved