List of pairs (m,2m) where m is the least unused positive number.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =4a(5) =8a(6) =5a(7) =10a(8) =7a(9) =14a(10) =9a(11) =18a(12) =11a(13) =22a(14) =12a(15) =24a(16) =13a(17) =26a(18) =15a(19) =30a(20) =16a(21) =32a(22) =17a(23) =34a(24) =19a(25) =38a(26) =20a(27) =40a(28) =21a(29) =42