OFFSET
1,12
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
MAPLE
A318875 := n -> nops(select(d -> (2*numtheory:-phi(d)) < d, divisors(n))):
seq(A318875(n), n=1..199); # Peter Luschny, Sep 05 2018
MATHEMATICA
A318875[n_] := DivisorSum[n, 1 &, 2*EulerPhi[#] < # &];
Array[A318875, 100] (* Paolo Xausa, Jul 08 2024 *)
PROG
(PARI) A318875(n) = sumdiv(n, d, (2*eulerphi(d))<d);
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Sep 05 2018
STATUS
approved