OFFSET
1,2
LINKS
FORMULA
a(n) = Sum_{d|n} d / gcd(d, n/d).
From Amiram Eldar, Dec 05 2022: (Start)
Multiplicative with a(p^e) = (p^(e+2)-1)/(p^2-1) + e/2 if e is even, and (p^(e+2)-p)/(p^2-1) + (e + 1)/2 if e is odd.
Sum_{k=1..n} a(k) ~ c * n^2, where c = 7*zeta(6)/(8*zeta(5)) = 0.740543... . (End)
MAPLE
a:= n-> add(d/igcd(d, n/d), d=numtheory[divisors](n)):
seq(a(n), n=1..80); # Alois P. Heinz, Feb 17 2020
MATHEMATICA
Table[Sum[LCM[d, n/d]/d, {d, Divisors[n]}], {n, 1, 70}]
f[p_, e_] := If[EvenQ[e], (p^(e + 2) - 1)/(p^2 - 1) + e/2, (p^(e + 2) - p)/(p^2 - 1) + (e + 1)/2]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Dec 05 2022 *)
PROG
(PARI) A332619(n) = sumdiv(n, d, lcm(d, n/d)/d); \\ Antti Karttunen, Nov 12 2021
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
Ilya Gutkovskiy, Feb 17 2020
STATUS
approved