a(n) is the Wiener index of the Lucas cube L_n.

Terms

a(0) =0a(1) =4a(2) =9a(3) =40a(4) =120a(5) =390a(6) =1176a(7) =3536a(8) =10395a(9) =30260a(10) =87120a(11) =248844a(12) =705744a(13) =1989820a(14) =5581485a(15) =15586720a(16) =43356936a(17) =120187026a(18) =332134440a(19) =915304520a(20) =2516113215a(21) =6900949484a(22) =18888143904a(23) =51599794200a(24) =140718765600a(25) =383142771700