Triangle read by rows: numbers of isomers of unbranched a-4-catapolyheptagons.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =3a(8) =3a(9) =1a(10) =6a(11) =10a(12) =11a(13) =3a(14) =1a(15) =20a(16) =46a(17) =48a(18) =21a(19) =5a(20) =1a(21) =72a(22) =192a(23) =228a(24) =116a(25) =37a(26) =5a(27) =1a(28) =272a(29) =840