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A097914 Number of points in a certain complex manifold associated with the Hilbert modular group of the totally real field Q(sqrt(n)), n squarefree, that arise from isotropy groups of order 2. 2
1, 2, 3, 2, 6, 4, 6, 10, 2, 12, 8, 4, 10, 4, 6, 12, 18, 6, 12, 12, 4, 12, 20, 2, 18, 16, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..27.

F. Hirzebruch, Hilbert modular surfaces, L'Enseignement Math., 19 (1973), 183-281; Ges. Abh. II, 225-323.

A. Prestel, Die elliptischen Fixpunkte der Hilbertschen Modulgruppen, Math. Ann., 177 (1968), 181-209.

A. Prestel, Die Fixpunkte der symmetrischen Hilbertschen Modulgruppe zu einem reell-quadratischen Zahlk├Ârper mit Primzahldiskriminante, Math. Ann., 200 (1973), 123-139.

CROSSREFS

Cf. A097915, A097916, A097917, A097918.

Sequence in context: A197289 A161888 A157224 * A286633 A286586 A113710

Adjacent sequences:  A097911 A097912 A097913 * A097915 A097916 A097917

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane, Sep 04 2004

STATUS

approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)