OFFSET
1,3
COMMENTS
Not multiplicative as a(3) = 4, a(5) = 6 and a(7) = 8, but a(105) = 87, not a(3)*a(5)*a(7) = 4*6*8 = 192 = A000593(105).
LINKS
FORMULA
EXAMPLE
n = 105 has divisors [1, 3, 5, 7, 15, 21, 35, 105]. When A083254 is applied to them, all others except the last one result a positive number, thus a(105) = 1+3+5+7+15+21+35 = 87.
MATHEMATICA
A318876[n_] := DivisorSum[n, # &, 2*EulerPhi[#] > # &];
Array[A318876, 100] (* Paolo Xausa, Jul 08 2024 *)
PROG
(PARI) A318876(n) = sumdiv(n, d, ((2*eulerphi(d))>d)*d);
CROSSREFS
Cf. also A187793.
KEYWORD
nonn
AUTHOR
Antti Karttunen, Sep 05 2018
STATUS
approved