a(n) = 6*binomial(n,4) + 2*binomial(n,2) + 1.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =19a(5) =51a(6) =121a(7) =253a(8) =477a(9) =829a(10) =1351a(11) =2091a(12) =3103a(13) =4447a(14) =6189a(15) =8401a(16) =11161a(17) =14553a(18) =18667a(19) =23599a(20) =29451a(21) =36331a(22) =44353a(23) =53637a(24) =64309a(25) =76501a(26) =90351a(27) =106003a(28) =123607a(29) =143319