Number of benzenoids with 21 hexagons with C_(2v) symmetry containing n carbon atoms.

Terms

a(0) =1a(1) =7a(2) =12a(3) =70a(4) =36a(5) =235a(6) =167a(7) =867a(8) =517a(9) =2453a(10) =1262a(11) =6150a(12) =3642a(13) =16214a(14) =8863a(15) =37733a(16) =18149a(17) =75274a(18) =34783a(19) =138929a(20) =60330a(21) =239646a(22) =82662a(23) =335306a(24) =74046a(25) =311055a(26) =33940a(27) =152826a(28) =1635175