a(n) = Sum_{h=0..n, k=0..n} T(h,k), array T counting knights' moves as in A049604.

Terms

a(0) =0a(1) =10a(2) =20a(3) =38a(4) =62a(5) =100a(6) =150a(7) =220a(8) =302a(9) =410a(10) =536a(11) =692a(12) =868a(13) =1080a(14) =1316a(15) =1594a(16) =1898a(17) =2248a(18) =2630a(19) =3064a(20) =3530a(21) =4054a(22) =4616a(23) =5240a(24) =5904a(25) =6636a(26) =7412a(27) =8262a(28) =9158a(29) =10132