OFFSET
0,1
COMMENTS
Kekulé numbers for certain benzenoids. T(n,n) = 9n^2 + 28n + 20 = A051872(n+2).
REFERENCES
S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 102).
FORMULA
G.f.: (20 - 6z - 3t*z + t^2*z^2 - 16t*z^2 - 4t^2*z^3)/((1-z)^2*(1-t*z)^3).
EXAMPLE
Triangle begins:
20;
34,57;
48,80,112;
62,103,144,185;
MAPLE
T:=proc(n, k) if k<=n then 9*k*n+14*(n+k)+20 else 0 fi end: for n from 0 to 10 do seq(T(n, k), k=0..n) od; # yields sequence in triangular form
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Emeric Deutsch, Jun 14 2005
STATUS
approved