A370496 - cp's OEIS frontend

A370496 a(1) = 1; for n > 1, a(n) is smallest unused number such that a(n) is coprime to a(n-1) and sopfr(a(n)) is coprime to sopfr(a(n-1)), where sopfr(k) is the sum of the primes dividing k, with repetition.

n	a(n)
1	1
2	2
3	3
4	4
5	5
6	7
7	6
8	11
9	8
10	13
11	9
12	10
13	17
14	12
15	19
16	14
17	15
18	22
19	21
20	20
21	23
22	16
23	27
24	25
25	24
26	29
27	18
28	31
29	26
30	33
31	28
32	37
33	30
34	41
35	32
36	43
37	34
38	35
39	46
40	39
41	38
42	45
43	44
44	47
45	36
46	53
47	40
48	49
49	48
50	55
51	52
52	51
53	56
54	57
55	58
56	59
57	42
58	61
59	50
60	63
61	62
62	67
63	54
64	65
65	71
66	60
67	73
68	64
69	75
70	68
71	69
72	76
73	77
74	79
75	66
76	83
77	70

[1, 2, 3, 4, 5, 7, 6, 11, 8, 13, 9, 10, 17, 12, 19, 14, 15, 22, 21, 20, 23, 16, 27, 25, 24, 29, 18, 31, 26, 33, 28, 37, 30, 41, 32, 43, 34, 35, 46, 39, 38, 45, 44, 47, 36, 53, 40, 49, 48, 55, 52, 51, 56, 57, 58, 59, 42, 61, 50, 63, 62, 67, 54, 65, 71, 60, 73, 64, 75, 68, 69, 76, 77, 79, 66, 83, 70]

cp's OEIS Frontend

A370496 a(1) = 1; for n > 1, a(n) is smallest unused number such that a(n) is coprime to a(n-1) and sopfr(a(n)) is coprime to sopfr(a(n-1)), where sopfr(k) is the sum of the primes dividing k, with repetition.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	4
5	5
6	7
7	6
8	11
9	8
10	13
11	9
12	10
13	17
14	12
15	19
16	14
17	15
18	22
19	21
20	20
21	23
22	16
23	27
24	25
25	24
26	29
27	18
28	31
29	26
30	33
31	28
32	37
33	30
34	41
35	32
36	43
37	34
38	35
39	46
40	39
41	38
42	45
43	44
44	47
45	36
46	53
47	40
48	49
49	48
50	55
51	52
52	51
53	56
54	57
55	58
56	59
57	42
58	61
59	50
60	63
61	62
62	67
63	54
64	65
65	71
66	60
67	73
68	64
69	75
70	68
71	69
72	76
73	77
74	79
75	66
76	83
77	70

n	a(n)
1	1
2	2
3	3
4	4
5	5
6	7
7	6
8	11
9	8
10	13
11	9
12	10
13	17
14	12
15	19
16	14
17	15
18	22
19	21
20	20
21	23
22	16
23	27
24	25
25	24
26	29
27	18
28	31
29	26
30	33
31	28
32	37
33	30
34	41
35	32
36	43
37	34
38	35
39	46
40	39
41	38
42	45
43	44
44	47
45	36
46	53
47	40
48	49
49	48
50	55
51	52
52	51
53	56
54	57
55	58
56	59
57	42
58	61
59	50
60	63
61	62
62	67
63	54
64	65
65	71
66	60
67	73
68	64
69	75
70	68
71	69
72	76
73	77
74	79
75	66
76	83
77	70

n	a(n)
1	1
2	2
3	3
4	4
5	5
6	7
7	6
8	11
9	8
10	13
11	9
12	10
13	17
14	12
15	19
16	14
17	15
18	22
19	21
20	20
21	23
22	16
23	27
24	25
25	24
26	29
27	18
28	31
29	26
30	33
31	28
32	37
33	30
34	41
35	32
36	43
37	34
38	35
39	46
40	39
41	38
42	45
43	44
44	47
45	36
46	53
47	40
48	49
49	48
50	55
51	52
52	51
53	56
54	57
55	58
56	59
57	42
58	61
59	50
60	63
61	62
62	67
63	54
64	65
65	71
66	60
67	73
68	64
69	75
70	68
71	69
72	76
73	77
74	79
75	66
76	83
77	70