OFFSET
1,1
REFERENCES
Stephen P Humphries, "Cogrowth of groups and the Dedekind-Frobenius group determinant", Mathematical Proceeding Cambridge Philosophical Society, volume 121 Part 2, pages 193-217 (1997).
FORMULA
a(n) = 2 * 11^(n-1) + (-1)^(n/2) * 5 * 11^(n/2-1) * (cos(Pi*n) + 1) [from Humphries]. Sean A. Irvine, Feb 26 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Sean A. Irvine, Feb 26 2018
STATUS
approved