a(0) = 1, thereafter a(n) = 4n.

Terms

a(0) =1a(1) =4a(2) =8a(3) =12a(4) =16a(5) =20a(6) =24a(7) =28a(8) =32a(9) =36a(10) =40a(11) =44a(12) =48a(13) =52a(14) =56a(15) =60a(16) =64a(17) =68a(18) =72a(19) =76a(20) =80a(21) =84a(22) =88a(23) =92a(24) =96a(25) =100a(26) =104a(27) =108a(28) =112a(29) =116