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A027840
Number of subgroups of index n in fundamental group of a certain fiber space.
6
1, 15, 220, 5275, 151086, 6605004, 362069912, 26370058035, 2384037107365, 264380945199210, 35133143655934644, 5515729438742221708, 1009373492449379367974, 212997911074525038601560, 51337590023913924398371080, 14016616814674335739387516003
OFFSET
1,2
LINKS
Sean A. Irvine, Java program (github).
V. A. Liskovets and A. Mednykh, Enumeration of subgroups in the fundamental groups of orientable circle bundles over surfaces, Commun. in Algebra, 28, No. 4 (2000), 1717-1738.
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Third term corrected from 240 to 220, Aug 15 1999
More terms from Sean A. Irvine, Dec 07 2019
STATUS
approved