A318324 - OEIS

%I #5 Aug 24 2018 22:13:27

%S 1,1,1,2,1,1,1,2,2,1,1,2,1,1,1,8,1,2,1,2,1,1,1,1,2,1,2,2,1,1,1,8,1,1,

%T 1,4,1,1,1,1,1,1,1,2,2,1,1,8,2,2,1,2,1,1,1,1,1,1,1,1,1,1,2,16,1,1,1,2,

%U 1,1,1,4,1,1,2,2,1,1,1,8,8,1,1,1,1,1,1,1,1,1,1,2,1,1,1,4,1,2,2,4,1,1,1,1,1

%N Denominators of rational valued sequence whose Dirichlet convolution with itself yields A046523, smallest number with same prime signature as n.

%H Antti Karttunen, <a href="/A318324/b318324.txt">Table of n, a(n) for n = 1..16384</a>

%F a(n) = denominator of f(n), where f(1) = 1, f(n) = (1/2) * (A046523(n) - Sum_{d|n, d>1, d<n} f(d) * f(n/d)) for n > 1.

%o (PARI)

%o up_to = 16384;

%o A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); };  \\ From A046523

%o 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.

%o v318323_24 = DirSqrt(vector(up_to, n, A046523(n)));

%o A318324(n) = denominator(v318323_24[n]);

%Y Cf. A046523, A318323 (numerators).

%K nonn,frac

%O 1,4

%A _Antti Karttunen_, Aug 24 2018