OFFSET
0,4
COMMENTS
The graph is empty for n = 0, 1 and 2, so a(n) = 0 by convention (or should it be 1?).
REFERENCES
A. Iranmanesh and A. Jafarzadeh, On the commuting graph associated with the symmetric and alternating groups, J. Algebra and Applic., 7 (2008), 129-146.
FORMULA
Conjecture: a(n) = a(n-1)+3*a(n-3)-3*a(n-4) for n>6. G.f.: -x^3*(x^6-x^5+2*x^3-x^2-x-2) / ((x-1)*(3*x^3-1)). - Colin Barker, Jul 26 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 07 2008
STATUS
approved