OFFSET
1,16
COMMENTS
No zeros among the first 2^20 terms. This is most probably multiplicative, like A318498.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
a(n) = numerator of f(n), where f(1) = 1, f(n) = (1/2) * (A061389(n) - Sum_{d|n, d>1, d<n} f(d) * f(n/d)) for n > 1.
PROG
(PARI)
up_to = 65537;
A061389(n) = factorback(apply(e -> (1+eulerphi(e)), factor(n)[, 2]));
DirSqrt(v) = {my(n=#v, u=vector(n)); u[1]=1; for(n=2, n, u[n]=(v[n]/v[1] - sumdiv(n, d, if(d>1&&d<n, u[d]*u[n/d], 0)))/2); u}; \\ From A317937.
v318497_98 = DirSqrt(vector(up_to, n, A061389(n)));
A318497(n) = numerator(v318497_98[n]);
CROSSREFS
KEYWORD
sign,frac
AUTHOR
Antti Karttunen, Aug 30 2018
STATUS
approved