Number of vertices in a "frame" of size n X n (see Comments in A331776 for definition).

Terms

a(0) =5a(1) =27a(2) =152a(3) =364a(4) =776a(5) =1340a(6) =2272a(7) =3532a(8) =5336a(9) =7516a(10) =10592a(11) =14316a(12) =19328a(13) =25100a(14) =32176a(15) =40428a(16) =50848a(17) =62476a(18) =76824a(19) =93020a(20) =111880a(21) =132492a(22) =157056a(23) =184140a(24) =215552a(25) =249452a(26) =287928a(27) =329900a(28) =378216a(29) =429852