OFFSET
2,1
LINKS
Sean A. Irvine, Java program (github)
J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.
FORMULA
For large n, (3.2143)^n < a(n) < (6.4188)^n (Th. 23.1.) - C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 17 2005
Conjectures from Colin Barker, Dec 20 2019: (Start)
G.f.: 2*x^2*(9 + 33*x + 8*x^2 - 12*x^3) / ((1 + x)*(1 + 2*x)*(1 - 5*x + 2*x^2)).
a(n) = 2*a(n-1) + 11*a(n-2) + 4*a(n-3) - 4*a(n-4) for n>5.
(End)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
a(6)-a(18) from Sean A. Irvine, Apr 30 2019
STATUS
approved