A173978 - cp's OEIS frontend

A173978 Numbers n such that the least prime factor of 2n - 3 is less than that of 2n - 1, unless 2n - 3 and 2n - 1 are (twin) primes.

n	a(n)
1	2
2	6
3	9
4	12
5	15
6	18
7	19
8	21
9	24
10	27
11	30
12	33
13	34
14	36
15	39
16	40
17	42
18	45
19	48
20	49
21	51
22	54
23	57
24	60
25	61
26	63
27	64
28	66
29	69
30	72
31	75
32	78
33	79
34	81
35	82
36	84
37	87
38	90
39	93
40	94
41	96
42	99
43	102
44	105
45	106
46	108
47	109
48	111
49	112
50	114
51	117
52	120
53	123
54	124

[2, 6, 9, 12, 15, 18, 19, 21, 24, 27, 30, 33, 34, 36, 39, 40, 42, 45, 48, 49, 51, 54, 57, 60, 61, 63, 64, 66, 69, 72, 75, 78, 79, 81, 82, 84, 87, 90, 93, 94, 96, 99, 102, 105, 106, 108, 109, 111, 112, 114, 117, 120, 123, 124]

cp's OEIS Frontend

A173978 Numbers n such that the least prime factor of 2n - 3 is less than that of 2n - 1, unless 2n - 3 and 2n - 1 are (twin) primes.

Table of values

List of values

n	a(n)
1	2
2	6
3	9
4	12
5	15
6	18
7	19
8	21
9	24
10	27
11	30
12	33
13	34
14	36
15	39
16	40
17	42
18	45
19	48
20	49
21	51
22	54
23	57
24	60
25	61
26	63
27	64
28	66
29	69
30	72
31	75
32	78
33	79
34	81
35	82
36	84
37	87
38	90
39	93
40	94
41	96
42	99
43	102
44	105
45	106
46	108
47	109
48	111
49	112
50	114
51	117
52	120
53	123
54	124

n	a(n)
1	2
2	6
3	9
4	12
5	15
6	18
7	19
8	21
9	24
10	27
11	30
12	33
13	34
14	36
15	39
16	40
17	42
18	45
19	48
20	49
21	51
22	54
23	57
24	60
25	61
26	63
27	64
28	66
29	69
30	72
31	75
32	78
33	79
34	81
35	82
36	84
37	87
38	90
39	93
40	94
41	96
42	99
43	102
44	105
45	106
46	108
47	109
48	111
49	112
50	114
51	117
52	120
53	123
54	124

n	a(n)
1	2
2	6
3	9
4	12
5	15
6	18
7	19
8	21
9	24
10	27
11	30
12	33
13	34
14	36
15	39
16	40
17	42
18	45
19	48
20	49
21	51
22	54
23	57
24	60
25	61
26	63
27	64
28	66
29	69
30	72
31	75
32	78
33	79
34	81
35	82
36	84
37	87
38	90
39	93
40	94
41	96
42	99
43	102
44	105
45	106
46	108
47	109
48	111
49	112
50	114
51	117
52	120
53	123
54	124