A286472 - cp's OEIS frontend

A286472 Compound filter (for counting prime gaps): a(1) = 1, a(n) = 2*A032742(n) + (1 if n is composite and spf(A032742(n)) > nextprime(spf(n)), and 0 otherwise). Here spf is the smallest prime factor, A020639.

n	a(n)
1	1
2	2
3	2
4	4
5	2
6	6
7	2
8	8
9	6
10	11
11	2
12	12
13	2
14	15
15	10
16	16
17	2
18	18
19	2
20	20
21	15
22	23
23	2
24	24
25	10
26	27
27	18
28	28
29	2
30	30
31	2
32	32
33	23
34	35
35	14
36	36
37	2
38	39
39	27
40	40
41	2
42	42
43	2
44	44
45	30
46	47
47	2
48	48
49	14
50	51
51	35
52	52
53	2
54	54
55	23
56	56
57	39
58	59
59	2
60	60
61	2
62	63
63	42
64	64
65	27
66	66
67	2
68	68
69	47
70	71
71	2
72	72
73	2
74	75
75	50
76	76
77	22
78	78
79	2

[1, 2, 2, 4, 2, 6, 2, 8, 6, 11, 2, 12, 2, 15, 10, 16, 2, 18, 2, 20, 15, 23, 2, 24, 10, 27, 18, 28, 2, 30, 2, 32, 23, 35, 14, 36, 2, 39, 27, 40, 2, 42, 2, 44, 30, 47, 2, 48, 14, 51, 35, 52, 2, 54, 23, 56, 39, 59, 2, 60, 2, 63, 42, 64, 27, 66, 2, 68, 47, 71, 2, 72, 2, 75, 50, 76, 22, 78, 2]

cp's OEIS Frontend

A286472 Compound filter (for counting prime gaps): a(1) = 1, a(n) = 2*A032742(n) + (1 if n is composite and spf(A032742(n)) > nextprime(spf(n)), and 0 otherwise). Here spf is the smallest prime factor, A020639.

Table of values

List of values

n	a(n)
1	1
2	2
3	2
4	4
5	2
6	6
7	2
8	8
9	6
10	11
11	2
12	12
13	2
14	15
15	10
16	16
17	2
18	18
19	2
20	20
21	15
22	23
23	2
24	24
25	10
26	27
27	18
28	28
29	2
30	30
31	2
32	32
33	23
34	35
35	14
36	36
37	2
38	39
39	27
40	40
41	2
42	42
43	2
44	44
45	30
46	47
47	2
48	48
49	14
50	51
51	35
52	52
53	2
54	54
55	23
56	56
57	39
58	59
59	2
60	60
61	2
62	63
63	42
64	64
65	27
66	66
67	2
68	68
69	47
70	71
71	2
72	72
73	2
74	75
75	50
76	76
77	22
78	78
79	2

n	a(n)
1	1
2	2
3	2
4	4
5	2
6	6
7	2
8	8
9	6
10	11
11	2
12	12
13	2
14	15
15	10
16	16
17	2
18	18
19	2
20	20
21	15
22	23
23	2
24	24
25	10
26	27
27	18
28	28
29	2
30	30
31	2
32	32
33	23
34	35
35	14
36	36
37	2
38	39
39	27
40	40
41	2
42	42
43	2
44	44
45	30
46	47
47	2
48	48
49	14
50	51
51	35
52	52
53	2
54	54
55	23
56	56
57	39
58	59
59	2
60	60
61	2
62	63
63	42
64	64
65	27
66	66
67	2
68	68
69	47
70	71
71	2
72	72
73	2
74	75
75	50
76	76
77	22
78	78
79	2

n	a(n)
1	1
2	2
3	2
4	4
5	2
6	6
7	2
8	8
9	6
10	11
11	2
12	12
13	2
14	15
15	10
16	16
17	2
18	18
19	2
20	20
21	15
22	23
23	2
24	24
25	10
26	27
27	18
28	28
29	2
30	30
31	2
32	32
33	23
34	35
35	14
36	36
37	2
38	39
39	27
40	40
41	2
42	42
43	2
44	44
45	30
46	47
47	2
48	48
49	14
50	51
51	35
52	52
53	2
54	54
55	23
56	56
57	39
58	59
59	2
60	60
61	2
62	63
63	42
64	64
65	27
66	66
67	2
68	68
69	47
70	71
71	2
72	72
73	2
74	75
75	50
76	76
77	22
78	78
79	2