OFFSET
1,2
COMMENTS
Multiplicative because A003961 is.
LINKS
FORMULA
a(n) = numerator of f(n), where f(1) = 1, f(n) = (1/2) * (A003961(n) - Sum_{d|n, d>1, d<n} f(d) * f(n/d)) for n > 1.
PROG
(PARI)
up_to = 16384;
A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
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.
v318321aux = DirSqrt(vector(up_to, n, A003961(n)));
A318321(n) = numerator(v318321aux[n]);
CROSSREFS
KEYWORD
nonn,frac,mult
AUTHOR
Antti Karttunen, Aug 24 2018
STATUS
approved