Triangular numbers + 1 squared.

Terms

a(0) =1a(1) =4a(2) =16a(3) =49a(4) =121a(5) =256a(6) =484a(7) =841a(8) =1369a(9) =2116a(10) =3136a(11) =4489a(12) =6241a(13) =8464a(14) =11236a(15) =14641a(16) =18769a(17) =23716a(18) =29584a(19) =36481a(20) =44521a(21) =53824a(22) =64516a(23) =76729a(24) =90601a(25) =106276a(26) =123904a(27) =143641a(28) =165649a(29) =190096