OFFSET
1,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..5000
FORMULA
a(n) is multiplicative with a(p^e) = (p-1)*p^(2e-1)/2.
Sum_{k>=1} 1/a(k) = Product_{primes p} (1 + 2*p/((p-1)^2 * (p+1))) = 3.96555686901754604330173765246769123681199917183404752314230450571038281... - Vaclav Kotesovec, Sep 20 2020
MATHEMATICA
Table[n*EulerPhi[n]/2^PrimeNu[n], {n, 60}] (* G. C. Greubel, May 22 2017 *)
PROG
(Magma) [(n*EulerPhi(n)/2)/(2^((#(PrimeDivisors(n)))-1)): n in [1..100]]
(PARI) A248003(n) = n*eulerphi(n)/2^omega(n); \\ G. C. Greubel, May 22 2017; Jul 13 2024
(SageMath)
def A248003(n): return int(n*euler_phi(n)/2^(gp.omega(n)))
[A248003(n) for n in range(1, 61)] # G. C. Greubel, Jul 13 2024
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
Jaroslav Krizek, Sep 29 2014
STATUS
approved