Number of (non-null) connected induced subgraphs in the 2 X n king graph.

Terms

a(0) =3a(1) =15a(2) =54a(3) =174a(4) =537a(5) =1629a(6) =4908a(7) =14748a(8) =44271a(9) =132843a(10) =398562a(11) =1195722a(12) =3587205a(13) =10761657a(14) =32285016a(15) =96855096a(16) =290565339a(17) =871696071a(18) =2615088270a(19) =7845264870a(20) =23535794673a(21) =70607384085a(22) =211822152324a(23) =635466457044