A027840 Number of subgroups of index n in fundamental group of a certain fiber space.

1, 15, 220, 5275, 151086, 6605004, 362069912, 26370058035, 2384037107365, 264380945199210, 35133143655934644, 5515729438742221708, 1009373492449379367974, 212997911074525038601560, 51337590023913924398371080, 14016616814674335739387516003

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

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

Cf. A027838, A027839, A027841, A060240.

Extensions

Third term corrected from 240 to 220, Aug 15 1999

More terms from Sean A. Irvine, Dec 07 2019