OFFSET
1,2
LINKS
FORMULA
a(n) = denominator of f(n), where f(1) = 1, f(n) = (1/2) * (A000203(n) - Sum_{d|n, d>1, d<n} f(d) * f(n/d)) for n > 1.
PROG
(PARI)
A317831perA317832(n) = if(1==n, n, (sigma(n)-sumdiv(n, d, if((d>1)&&(d<n), A317831perA317832(d)*A317831perA317832(n/d), 0)))/2);
A317832(n) = denominator(A317831perA317832(n));
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Antti Karttunen, Aug 10 2018
STATUS
approved