A003278 - cp's OEIS frontend

A003278 Szekeres's sequence: a(n)-1 in ternary = n-1 in binary; also: a(1) = 1, a(2) = 2, and thereafter a(n) is smallest number k which avoids any 3-term arithmetic progression in a(1), a(2), ..., a(n-1), k.

n	a(n)
1	1
2	2
3	4
4	5
5	10
6	11
7	13
8	14
9	28
10	29
11	31
12	32
13	37
14	38
15	40
16	41
17	82
18	83
19	85
20	86
21	91
22	92
23	94
24	95
25	109
26	110
27	112
28	113
29	118
30	119
31	121
32	122
33	244
34	245
35	247
36	248
37	253
38	254
39	256
40	257
41	271
42	272
43	274
44	275
45	280
46	281
47	283
48	284
49	325
50	326
51	328
52	329
53	334
54	335
55	337
56	338
57	352
58	353

[1, 2, 4, 5, 10, 11, 13, 14, 28, 29, 31, 32, 37, 38, 40, 41, 82, 83, 85, 86, 91, 92, 94, 95, 109, 110, 112, 113, 118, 119, 121, 122, 244, 245, 247, 248, 253, 254, 256, 257, 271, 272, 274, 275, 280, 281, 283, 284, 325, 326, 328, 329, 334, 335, 337, 338, 352, 353]

cp's OEIS Frontend

A003278 Szekeres's sequence: a(n)-1 in ternary = n-1 in binary; also: a(1) = 1, a(2) = 2, and thereafter a(n) is smallest number k which avoids any 3-term arithmetic progression in a(1), a(2), ..., a(n-1), k.

Table of values

List of values

n	a(n)
1	1
2	2
3	4
4	5
5	10
6	11
7	13
8	14
9	28
10	29
11	31
12	32
13	37
14	38
15	40
16	41
17	82
18	83
19	85
20	86
21	91
22	92
23	94
24	95
25	109
26	110
27	112
28	113
29	118
30	119
31	121
32	122
33	244
34	245
35	247
36	248
37	253
38	254
39	256
40	257
41	271
42	272
43	274
44	275
45	280
46	281
47	283
48	284
49	325
50	326
51	328
52	329
53	334
54	335
55	337
56	338
57	352
58	353

n	a(n)
1	1
2	2
3	4
4	5
5	10
6	11
7	13
8	14
9	28
10	29
11	31
12	32
13	37
14	38
15	40
16	41
17	82
18	83
19	85
20	86
21	91
22	92
23	94
24	95
25	109
26	110
27	112
28	113
29	118
30	119
31	121
32	122
33	244
34	245
35	247
36	248
37	253
38	254
39	256
40	257
41	271
42	272
43	274
44	275
45	280
46	281
47	283
48	284
49	325
50	326
51	328
52	329
53	334
54	335
55	337
56	338
57	352
58	353

n	a(n)
1	1
2	2
3	4
4	5
5	10
6	11
7	13
8	14
9	28
10	29
11	31
12	32
13	37
14	38
15	40
16	41
17	82
18	83
19	85
20	86
21	91
22	92
23	94
24	95
25	109
26	110
27	112
28	113
29	118
30	119
31	121
32	122
33	244
34	245
35	247
36	248
37	253
38	254
39	256
40	257
41	271
42	272
43	274
44	275
45	280
46	281
47	283
48	284
49	325
50	326
51	328
52	329
53	334
54	335
55	337
56	338
57	352
58	353