OFFSET
1,2
LINKS
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.
FORMULA
a(n) = Sum_{m|n} A027840(m) * (n/m)^(2*m+2). - Sean A. Irvine, Dec 07 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Sean A. Irvine, Dec 07 2019
STATUS
approved