Maximum number of connections for a 2 X n rectangle.

Terms

a(0) =1a(1) =5a(2) =22a(3) =54a(4) =134a(5) =269a(6) =534a(7) =934a(8) =1618a(9) =2573a(10) =4062a(11) =6030a(12) =8902a(13) =12549a(14) =17614a(15) =23854a(16) =32194a(17) =42229a(18) =55238