Number of vertices in a regular drawing of the complete bipartite graph K_{n,n}.

Terms

a(0) =2a(1) =5a(2) =13a(3) =35a(4) =75a(5) =159a(6) =275a(7) =477a(8) =755a(9) =1163a(10) =1659a(11) =2373a(12) =3243a(13) =4429a(14) =5799a(15) =7489a(16) =9467a(17) =11981a(18) =14791a(19) =18275a(20) =22215a(21) =26815a(22) =31847a(23) =37861a(24) =44499a(25) =52213a(26) =60543a(27) =70011a(28) =80347a(29) =92263