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A121950
Number of isomeric aza-benzenoids with two nitrogen atoms and n hexagons.
0
3, 10, 48, 243, 1326, 7349, 41030, 228694, 1270663, 7031737
OFFSET
1,1
LINKS
N. Trinajstić, Ž. Jeričević, J. V. Knop, W. R. Müller and K. Szymanski, Computer generation of isomeric structures, Pure and Appl. Chem., vol. 55 (1983) pp. 379-390. See Table 6 on p. 387.
EXAMPLE
In a single hexagon (benzene), any 2 of the 6 carbon atoms can be chosen to be replaced by nitrogen, and it can be done in 3 ways, obtaining pyridazine, pyrimidine, or pyrazine, so a(1) = 3. For a(2) = 10, see the corresponding column of Table 7 from Trinajstić et al.
KEYWORD
nonn,more
AUTHOR
Parthasarathy Nambi, Sep 04 2006
EXTENSIONS
a(1) corrected by Andrey Zabolotskiy, Nov 19 2023
STATUS
approved