A213257 - cp's OEIS frontend

A213257 a(1) = 1, a(2) = 2 and, for n > 2, a(n) is the smallest integer greater than a(n - 1) such that no three terms of the sequence form a geometric progression of the form {x, 2 x, 4 x}.

n	a(n)
1	1
2	2
3	3
4	5
5	6
6	7
7	8
8	9
9	10
10	11
11	13
12	14
13	15
14	16
15	17
16	18
17	19
18	21
19	22
20	23
21	24
22	25
23	26
24	27
25	29
26	30
27	31
28	33
29	34
30	35
31	37
32	38
33	39
34	40
35	41
36	42
37	43
38	45
39	46
40	47
41	48
42	49
43	50
44	51
45	53
46	54
47	55
48	56
49	57
50	58
51	59
52	61
53	62
54	63
55	64
56	65
57	66
58	67
59	69
60	70
61	71
62	72
63	73
64	74
65	75
66	77
67	78
68	79
69	80
70	81
71	82
72	83
73	85
74	86
75	87
76	88
77	89
78	90
79	91
80	93
81	94
82	95
83	97
84	98
85	99
86	101
87	102
88	103
89	104
90	105

[1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 45, 46, 47, 48, 49, 50, 51, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 89, 90, 91, 93, 94, 95, 97, 98, 99, 101, 102, 103, 104, 105]

cp's OEIS Frontend

A213257 a(1) = 1, a(2) = 2 and, for n > 2, a(n) is the smallest integer greater than a(n - 1) such that no three terms of the sequence form a geometric progression of the form {x, 2 x, 4 x}.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	5
5	6
6	7
7	8
8	9
9	10
10	11
11	13
12	14
13	15
14	16
15	17
16	18
17	19
18	21
19	22
20	23
21	24
22	25
23	26
24	27
25	29
26	30
27	31
28	33
29	34
30	35
31	37
32	38
33	39
34	40
35	41
36	42
37	43
38	45
39	46
40	47
41	48
42	49
43	50
44	51
45	53
46	54
47	55
48	56
49	57
50	58
51	59
52	61
53	62
54	63
55	64
56	65
57	66
58	67
59	69
60	70
61	71
62	72
63	73
64	74
65	75
66	77
67	78
68	79
69	80
70	81
71	82
72	83
73	85
74	86
75	87
76	88
77	89
78	90
79	91
80	93
81	94
82	95
83	97
84	98
85	99
86	101
87	102
88	103
89	104
90	105

n	a(n)
1	1
2	2
3	3
4	5
5	6
6	7
7	8
8	9
9	10
10	11
11	13
12	14
13	15
14	16
15	17
16	18
17	19
18	21
19	22
20	23
21	24
22	25
23	26
24	27
25	29
26	30
27	31
28	33
29	34
30	35
31	37
32	38
33	39
34	40
35	41
36	42
37	43
38	45
39	46
40	47
41	48
42	49
43	50
44	51
45	53
46	54
47	55
48	56
49	57
50	58
51	59
52	61
53	62
54	63
55	64
56	65
57	66
58	67
59	69
60	70
61	71
62	72
63	73
64	74
65	75
66	77
67	78
68	79
69	80
70	81
71	82
72	83
73	85
74	86
75	87
76	88
77	89
78	90
79	91
80	93
81	94
82	95
83	97
84	98
85	99
86	101
87	102
88	103
89	104
90	105

n	a(n)
1	1
2	2
3	3
4	5
5	6
6	7
7	8
8	9
9	10
10	11
11	13
12	14
13	15
14	16
15	17
16	18
17	19
18	21
19	22
20	23
21	24
22	25
23	26
24	27
25	29
26	30
27	31
28	33
29	34
30	35
31	37
32	38
33	39
34	40
35	41
36	42
37	43
38	45
39	46
40	47
41	48
42	49
43	50
44	51
45	53
46	54
47	55
48	56
49	57
50	58
51	59
52	61
53	62
54	63
55	64
56	65
57	66
58	67
59	69
60	70
61	71
62	72
63	73
64	74
65	75
66	77
67	78
68	79
69	80
70	81
71	82
72	83
73	85
74	86
75	87
76	88
77	89
78	90
79	91
80	93
81	94
82	95
83	97
84	98
85	99
86	101
87	102
88	103
89	104
90	105