a(1)=2; for n > 1, a(n) is the largest number <= 2*a(n-1) divisible by n.

Terms

a(0) =2a(1) =4a(2) =6a(3) =12a(4) =20a(5) =36a(6) =70a(7) =136a(8) =270a(9) =540a(10) =1078a(11) =2148a(12) =4290a(13) =8568a(14) =17130a(15) =34256a(16) =68510a(17) =137016a(18) =274018a(19) =548020a(20) =1096032a(21) =2192058a(22) =4384099a(23) =8768184a(24) =17536350a(25) =35072700a(26) =70145379a(27) =140290752a(28) =280581496a(29) =561162990