OFFSET
1,3
LINKS
Felix Fröhlich, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = abs(A199084(n)).
a(2n+1) = 2n+1.
Sum_{k=1..n} a(k) ~ (n^2/Pi^2) * (log(n) + 2*gamma - 1/2 - 4*log(2)/3 + Pi^2/4 - zeta'(2)/zeta(2)), where gamma is Euler's constant (A001620). - Amiram Eldar, Mar 30 2024
PROG
(PARI) a(n) = sum(k=1, n, (-1)^(n-k)*gcd(k, n)); \\ Michel Marcus, May 16 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Max Alekseyev, May 16 2021
EXTENSIONS
More terms from Felix Fröhlich, May 19 2021
STATUS
approved