A095115 - cp's OEIS frontend

A095115 a(1)=1. Given a(1),...,a(n-1), to find a(n), let S = {a(1), ..., a(n-1), |a(2)-a(1)|, ..., |a(n-1)-a(n-2)|}. Let d be the smallest positive integer not in S. Then a(n) is the smallest one of a(n-1)-d and a(n-1)+d which is a positive integer not in S union {d}.

n	a(n)
1	1
2	3
3	7
4	12
5	18
6	10
7	19
8	30
9	17
10	31
11	16
12	36
13	57
14	35
15	58
16	34
17	59
18	33
19	60
20	32
21	61
22	98
23	136
24	97
25	137
26	96
27	54

[1, 3, 7, 12, 18, 10, 19, 30, 17, 31, 16, 36, 57, 35, 58, 34, 59, 33, 60, 32, 61, 98, 136, 97, 137, 96, 54]