OFFSET
1,3
LINKS
Jean-Louis Lascoux, Table of n, a(n) for n = 1..1001
FORMULA
a(n) = (n - 1) * Sum_{k=2..n} phi(k).
a(n) = (n - 1) * (A002088(n) - 1).
Asymptotic: a(n) ~ (3 / Pi^2) * n^3.
MAPLE
with(numtheory):
a := n -> (n-1)*add(phi(k), k=2..n):
seq(a(n), n=1..40);
MATHEMATICA
a[n_] := (n - 1) * Sum[EulerPhi[k], {k, 2, n}];
Array[a, 40, 1]
PROG
(Python)
import sympy as sp
def a(n): return (n-1)*sum(sp.totient(k) for k in range(2, n+1))
print([a(n) for n in range(1, 41)])
(PARI)
a(n)=my(s=0); for(k=2, n, s+=eulerphi(k)); (n-1)*s;
vector(40, j, a(j))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jean-Louis Lascoux, Nov 16 2025
STATUS
approved
