Restricted postage stamp problem with n denominations and 2 stamps.

Terms

a(0) =2a(1) =4a(2) =8a(3) =12a(4) =16a(5) =20a(6) =26a(7) =32a(8) =40a(9) =44a(10) =54a(11) =64a(12) =72a(13) =80a(14) =92a(15) =104a(16) =116a(17) =128a(18) =140a(19) =152a(20) =164a(21) =180a(22) =196a(23) =212a(24) =228a(25) =244a(26) =262a(27) =280a(28) =298a(29) =316