OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..5000
FORMULA
MAPLE
f:= n -> add(ceil(n/k)*igcd(n, k), k=1..n):
map(f, [$1..100]); # Robert Israel, Mar 24 2020
MATHEMATICA
Table[Sum[Ceiling[n/k] GCD[n, k], {k, n}], {n, 60}]
Table[Sum[EulerPhi[n/d] (d + Sum[DivisorSigma[0, k], {k, d - 1}]), {d, Divisors[n]}], {n, 60}]
PROG
(PARI) a(n) = sum(k=1, n, ceil(n/k)*gcd(n, k)); \\ Michel Marcus, Mar 23 2020
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Ilya Gutkovskiy, Mar 22 2020
STATUS
approved