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A318667
Numerators of the sequence whose Dirichlet convolution with itself yields A318307, which is multiplicative with A318307(p^e) = 2^A002487(e).
2
1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, -5, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 31, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, -5, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, -43, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, -5, -5, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 31, 1, 1, 1, 1, 1, 1, 1, 3, 1
OFFSET
1,8
COMMENTS
Multiplicative because A318307 and A317934 are.
LINKS
FORMULA
a(n) = numerator of f(n), where f(1) = 1, f(n) = (1/2) * (A318307(n) - Sum_{d|n, d>1, d<n} f(d) * f(n/d)) for n > 1.
PROG
(PARI)
up_to = 1+(2^16);
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};
A002487(n) = { my(a=1, b=0); while(n>0, if(bitand(n, 1), b+=a, a+=b); n>>=1); (b); }; \\ From A002487
A318307(n) = factorback(apply(e -> 2^A002487(e), factor(n)[, 2]));
v318667_aux = DirSqrt(vector(up_to, n, A318307(n)));
A318667(n) = numerator(v318667_aux[n]);
CROSSREFS
Cf. A318307, A317934 (denominators).
Sequence in context: A204114 A204131 A317941 * A365426 A030598 A030395
KEYWORD
sign,frac,mult
AUTHOR
Antti Karttunen, Sep 03 2018
STATUS
approved