A079406 Recaman variation: a(1)=1, then a(n)=a(n-1)-n if n is already in the sequence, a(n)=a(n-1)+n otherwise.

1, 3, 0, 4, 9, 15, 22, 30, 21, 31, 42, 54, 67, 81, 66, 82, 99, 117, 136, 156, 135, 113, 136, 160, 185, 211, 238, 266, 295, 265, 234, 266, 299, 333, 368, 404, 441, 479, 518, 558, 599, 557, 600, 644, 689, 735, 782, 830, 879, 929, 980, 1032, 1085, 1031, 1086, 1142