Triangle read by rows: T(n,k) is the number of labeled planar graphs on n vertices and k edges.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =3a(6) =3a(7) =1a(8) =1a(9) =6a(10) =15a(11) =20a(12) =15a(13) =6a(14) =1a(15) =1a(16) =10a(17) =45a(18) =120a(19) =210a(20) =252a(21) =210a(22) =120a(23) =45a(24) =10a(25) =1a(26) =15a(27) =105a(28) =455a(29) =1365