OFFSET
1,6
COMMENTS
It is known that a(n) >= 0 for n >= 1.
REFERENCES
D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 10.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
MATHEMATICA
Array[#2 + #3 (#1 - #2) - #4 & @@ {#, EulerPhi@ #, DivisorSigma[0, #], DivisorSigma[1, #]} &, 75] (* Michael De Vlieger, Feb 25 2018 *)
PROG
(PARI) A079540(n) = (eulerphi(n) + numdiv(n)*(n - eulerphi(n)) - sigma(n)); \\ Antti Karttunen, Feb 25 2018
(Magma) [EulerPhi(n) + DivisorSigma(0, n)*(n - EulerPhi(n)) - DivisorSigma(1, n): n in [1..80]]; // G. C. Greubel, Jan 15 2019
(Sage) [euler_phi(n) + sigma(n, 0)*(n - euler_phi(n)) - sigma(n, 1) for n in (1..80)] # G. C. Greubel, Jan 15 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 23 2003
STATUS
approved