Sum of the corners of a 2n+1 X 2n+1 square spiral.

Terms

a(0) =24a(1) =76a(2) =160a(3) =276a(4) =424a(5) =604a(6) =816a(7) =1060a(8) =1336a(9) =1644a(10) =1984a(11) =2356a(12) =2760a(13) =3196a(14) =3664a(15) =4164a(16) =4696a(17) =5260a(18) =5856a(19) =6484a(20) =7144a(21) =7836a(22) =8560a(23) =9316a(24) =10104a(25) =10924a(26) =11776a(27) =12660a(28) =13576a(29) =14524