Sequence and first differences (A030124) together list all positive numbers exactly once.

Terms

a(0) =1a(1) =3a(2) =7a(3) =12a(4) =18a(5) =26a(6) =35a(7) =45a(8) =56a(9) =69a(10) =83a(11) =98a(12) =114a(13) =131a(14) =150a(15) =170a(16) =191a(17) =213a(18) =236a(19) =260a(20) =285a(21) =312a(22) =340a(23) =369a(24) =399a(25) =430a(26) =462a(27) =495a(28) =529a(29) =565