A177961 - cp's OEIS frontend

A177961 a(1)=2. Otherwise the average of the smallest prime divisors of 2n-1 and 2n+1.

n	a(n)
1	2
2	4
3	6
4	5
5	7
6	12
7	8
8	10
9	18
10	11
11	13
12	14
13	4
14	16
15	30
16	17
17	4
18	21
19	20
20	22
21	42
22	23
23	25
24	27
25	5
26	28
27	29
28	4
29	31
30	60
31	32
32	4
33	36
34	35
35	37
36	72
37	38
38	5
39	43
40	41
41	43
42	44
43	4
44	46
45	48
46	5
47	4
48	51
49	50
50	52
51	102
52	53
53	55
54	108
55	56
56	58
57	59
58	4
59	5
60	9
61	7
62	4
63	66
64	65
65	67
66	69
67	5
68	70
69	138
70	71
71	7
72	8
73	4
74	76
75	150
76	77
77	4
78	81

[2, 4, 6, 5, 7, 12, 8, 10, 18, 11, 13, 14, 4, 16, 30, 17, 4, 21, 20, 22, 42, 23, 25, 27, 5, 28, 29, 4, 31, 60, 32, 4, 36, 35, 37, 72, 38, 5, 43, 41, 43, 44, 4, 46, 48, 5, 4, 51, 50, 52, 102, 53, 55, 108, 56, 58, 59, 4, 5, 9, 7, 4, 66, 65, 67, 69, 5, 70, 138, 71, 7, 8, 4, 76, 150, 77, 4, 81]

cp's OEIS Frontend

A177961 a(1)=2. Otherwise the average of the smallest prime divisors of 2n-1 and 2n+1.

Table of values

List of values

n	a(n)
1	2
2	4
3	6
4	5
5	7
6	12
7	8
8	10
9	18
10	11
11	13
12	14
13	4
14	16
15	30
16	17
17	4
18	21
19	20
20	22
21	42
22	23
23	25
24	27
25	5
26	28
27	29
28	4
29	31
30	60
31	32
32	4
33	36
34	35
35	37
36	72
37	38
38	5
39	43
40	41
41	43
42	44
43	4
44	46
45	48
46	5
47	4
48	51
49	50
50	52
51	102
52	53
53	55
54	108
55	56
56	58
57	59
58	4
59	5
60	9
61	7
62	4
63	66
64	65
65	67
66	69
67	5
68	70
69	138
70	71
71	7
72	8
73	4
74	76
75	150
76	77
77	4
78	81

n	a(n)
1	2
2	4
3	6
4	5
5	7
6	12
7	8
8	10
9	18
10	11
11	13
12	14
13	4
14	16
15	30
16	17
17	4
18	21
19	20
20	22
21	42
22	23
23	25
24	27
25	5
26	28
27	29
28	4
29	31
30	60
31	32
32	4
33	36
34	35
35	37
36	72
37	38
38	5
39	43
40	41
41	43
42	44
43	4
44	46
45	48
46	5
47	4
48	51
49	50
50	52
51	102
52	53
53	55
54	108
55	56
56	58
57	59
58	4
59	5
60	9
61	7
62	4
63	66
64	65
65	67
66	69
67	5
68	70
69	138
70	71
71	7
72	8
73	4
74	76
75	150
76	77
77	4
78	81

n	a(n)
1	2
2	4
3	6
4	5
5	7
6	12
7	8
8	10
9	18
10	11
11	13
12	14
13	4
14	16
15	30
16	17
17	4
18	21
19	20
20	22
21	42
22	23
23	25
24	27
25	5
26	28
27	29
28	4
29	31
30	60
31	32
32	4
33	36
34	35
35	37
36	72
37	38
38	5
39	43
40	41
41	43
42	44
43	4
44	46
45	48
46	5
47	4
48	51
49	50
50	52
51	102
52	53
53	55
54	108
55	56
56	58
57	59
58	4
59	5
60	9
61	7
62	4
63	66
64	65
65	67
66	69
67	5
68	70
69	138
70	71
71	7
72	8
73	4
74	76
75	150
76	77
77	4
78	81