Number of connected induced (non-null) subgraphs of the prism graph with 2n nodes.

Terms

a(0) =3a(1) =13a(2) =51a(3) =167a(4) =503a(5) =1441a(6) =4007a(7) =10923a(8) =29355a(9) =78037a(10) =205659a(11) =538127a(12) =1399583a(13) =3621289a(14) =9327695a(15) =23931603a(16) =61186131a(17) =155949085a(18) =396369795a(19) =1004904695a(20) =2541896519a(21) =6416348209a(22) =16165610999a(23) =40657256571a(24) =102090514683a(25) =255968753125a(26) =640899345579