OFFSET
0,5
COMMENTS
REFERENCES
B. de Bivort. Isotemporal classes of diasters, beachballs and daisies. Preprint, 2005.
FORMULA
if k=0|n a(n, k)=1 if k=n/2 a(n, k)=(1/2)(k^2+3k+2) else a(n, k)=(n-k)k+(n-k)+k+1
EXAMPLE
Row 0 has 1 element, a diaster with no peripheral edges - a singleton edge - for which there is only a single isotemporal class. Row 1 has 2 elements, the diaster with a single peripheral edge on the left and the diaster with the single peripheral edge on the right - two edges sharing a single vertex - for each, there is a single isotemporal class. Row 2 has 3 elements, corresponding to the diaster with a two peripheral edges on the left, the diaster with a single peripheral edge on either side and the diaster with both peripheral edges on the right. These graphs have 1, 3 and 1 isotemporal classes respectively.
CROSSREFS
KEYWORD
easy,nonn,tabf
AUTHOR
Benjamin de Bivort (bivort(AT)fas.harvard.edu), Aug 04 2005
STATUS
approved