A375828 - cp's OEIS frontend

A375828 a(1) = 1; for n > 1, a(n) is the smallest unused positive number such that (a(n-1) AND a(n)) = a(n-1) if a(n-1) is prime, otherwise (a(n-1) AND a(n)) = 0, where AND is the binary AND operation.

n	a(n)
1	1
2	2
3	3
4	7
5	15
6	16
7	4
8	8
9	5
10	13
11	29
12	31
13	63
14	64
15	6
16	9
17	18
18	12
19	17
20	19
21	23
22	55
23	72
24	20
25	10
26	21
27	32
28	11
29	27
30	36
31	24
32	33
33	14
34	48
35	65
36	22
37	40
38	66
39	25
40	34
41	28
42	35
43	68
44	26
45	37
46	39
47	80
48	38
49	73
50	75
51	52
52	67
53	71
54	79
55	95
56	128
57	30
58	96
59	129
60	42
61	69
62	50
63	76
64	49
65	70
66	41
67	43
68	47
69	111
70	144
71	44
72	81
73	46
74	145
75	74
76	53
77	61
78	125
79	130
80	45
81	82
82	132
83	51
84	136
85	54
86	137
87	139
88	143
89	112

[1, 2, 3, 7, 15, 16, 4, 8, 5, 13, 29, 31, 63, 64, 6, 9, 18, 12, 17, 19, 23, 55, 72, 20, 10, 21, 32, 11, 27, 36, 24, 33, 14, 48, 65, 22, 40, 66, 25, 34, 28, 35, 68, 26, 37, 39, 80, 38, 73, 75, 52, 67, 71, 79, 95, 128, 30, 96, 129, 42, 69, 50, 76, 49, 70, 41, 43, 47, 111, 144, 44, 81, 46, 145, 74, 53, 61, 125, 130, 45, 82, 132, 51, 136, 54, 137, 139, 143, 112]

cp's OEIS Frontend

A375828 a(1) = 1; for n > 1, a(n) is the smallest unused positive number such that (a(n-1) AND a(n)) = a(n-1) if a(n-1) is prime, otherwise (a(n-1) AND a(n)) = 0, where AND is the binary AND operation.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	7
5	15
6	16
7	4
8	8
9	5
10	13
11	29
12	31
13	63
14	64
15	6
16	9
17	18
18	12
19	17
20	19
21	23
22	55
23	72
24	20
25	10
26	21
27	32
28	11
29	27
30	36
31	24
32	33
33	14
34	48
35	65
36	22
37	40
38	66
39	25
40	34
41	28
42	35
43	68
44	26
45	37
46	39
47	80
48	38
49	73
50	75
51	52
52	67
53	71
54	79
55	95
56	128
57	30
58	96
59	129
60	42
61	69
62	50
63	76
64	49
65	70
66	41
67	43
68	47
69	111
70	144
71	44
72	81
73	46
74	145
75	74
76	53
77	61
78	125
79	130
80	45
81	82
82	132
83	51
84	136
85	54
86	137
87	139
88	143
89	112

n	a(n)
1	1
2	2
3	3
4	7
5	15
6	16
7	4
8	8
9	5
10	13
11	29
12	31
13	63
14	64
15	6
16	9
17	18
18	12
19	17
20	19
21	23
22	55
23	72
24	20
25	10
26	21
27	32
28	11
29	27
30	36
31	24
32	33
33	14
34	48
35	65
36	22
37	40
38	66
39	25
40	34
41	28
42	35
43	68
44	26
45	37
46	39
47	80
48	38
49	73
50	75
51	52
52	67
53	71
54	79
55	95
56	128
57	30
58	96
59	129
60	42
61	69
62	50
63	76
64	49
65	70
66	41
67	43
68	47
69	111
70	144
71	44
72	81
73	46
74	145
75	74
76	53
77	61
78	125
79	130
80	45
81	82
82	132
83	51
84	136
85	54
86	137
87	139
88	143
89	112

n	a(n)
1	1
2	2
3	3
4	7
5	15
6	16
7	4
8	8
9	5
10	13
11	29
12	31
13	63
14	64
15	6
16	9
17	18
18	12
19	17
20	19
21	23
22	55
23	72
24	20
25	10
26	21
27	32
28	11
29	27
30	36
31	24
32	33
33	14
34	48
35	65
36	22
37	40
38	66
39	25
40	34
41	28
42	35
43	68
44	26
45	37
46	39
47	80
48	38
49	73
50	75
51	52
52	67
53	71
54	79
55	95
56	128
57	30
58	96
59	129
60	42
61	69
62	50
63	76
64	49
65	70
66	41
67	43
68	47
69	111
70	144
71	44
72	81
73	46
74	145
75	74
76	53
77	61
78	125
79	130
80	45
81	82
82	132
83	51
84	136
85	54
86	137
87	139
88	143
89	112