Iterates of A122237 starting from the initial value 6.

Terms

a(0) =6a(1) =18a(2) =48a(3) =141a(4) =431a(5) =1427a(6) =4692a(7) =15417a(8) =52833a(9) =189576a(10) =667458a(11) =2303485a(12) =8261483a(13) =30854617a(14) =112235989a(15) =396544978a(16) =1457813051a(17) =5573491517a(18) =20668205325a(19) =74283571059a(20) =277368667214