Boundary area of the T-square fractal.

Terms

a(0) =4a(1) =24a(2) =80a(3) =248a(4) =768a(5) =2360a(6) =7200a(7) =21848a(8) =66048a(9) =199160a(10) =599520a(11) =1802648a(12) =5416128a(13) =16264760a(14) =48827040a(15) =146546648a(16) =439771008a(17) =1319575160a(18) =3959249760a(19) =11878797848a(20) =35638490688a(21) =106919666360a(22) =320767387680a(23) =962318940248