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A097917
Denominator of 2*zeta_K(-1) where K is the totally real field Q(sqrt(n)), as n runs through the squarefree numbers.
5
6, 3, 15, 1, 3, 3, 3, 3, 3, 1, 3, 3, 3, 3, 3, 3, 1, 3, 3, 1, 3, 3, 3, 3, 3, 3, 1, 1, 3, 3, 1, 3, 3, 3, 1, 3, 3, 1, 3, 3, 1, 1, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 3, 1, 3, 3, 3, 3, 3, 1, 1, 1, 3, 1, 3, 3, 1, 1, 3, 3, 3, 1, 1, 3, 3, 3, 1, 3, 3, 1, 3, 1, 1, 1, 3, 3, 3, 3, 1, 3, 3, 3, 3
OFFSET
1,1
REFERENCES
F. Hirzebruch, Hilbert modular surfaces, Ges. Abh. II, 225-323.
LINKS
F. Hirzebruch, Hilbert modular surfaces, L'Enseignement Math., 19 (1973), 183-281. See p. 200.
EXAMPLE
1/6, 1/3, 1/15, 1, 4/3, 7/3, 7/3, 1/3, 10/3, 4, ...
PROG
(Sage) [(round(60*QuadraticField(d).zeta_function(100)(-1).real())/30).denominator() for d in range(2, 100) if Integer(d).is_squarefree()] # Robin Visser, Feb 28 2024
(PARI)
z(d) = -(1/2)*bernfrac(2)*d*sum(k=1, d-1, kronecker(d, k)*subst(bernpol(2), x, k/d)*(-1/2))
{v=[]; for(k=2, 100, if(issquarefree(k), my(d=k); if(k%4 <> 1, d = 4*k); v=concat(v, denominator(2*z(d)) ))); v} \\ Thomas Scheuerle, Feb 28 2024
CROSSREFS
Cf. A097916.
Sequence in context: A345056 A049784 A341746 * A116570 A335567 A362625
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Sep 04 2004
EXTENSIONS
More terms from Robin Visser, Feb 28 2024
STATUS
approved