A250480 - cp's OEIS frontend

A250480 a(1) = 0, and for n > 1: if n is a prime, a(n) = n, otherwise a(n) = A020639(n) - 1, where A020639(n) gives the least prime dividing n.

n	a(n)
1	0
2	2
3	3
4	1
5	5
6	1
7	7
8	1
9	2
10	1
11	11
12	1
13	13
14	1
15	2
16	1
17	17
18	1
19	19
20	1
21	2
22	1
23	23
24	1
25	4
26	1
27	2
28	1
29	29
30	1
31	31
32	1
33	2
34	1
35	4
36	1
37	37
38	1
39	2
40	1
41	41
42	1
43	43
44	1
45	2
46	1
47	47
48	1
49	6
50	1
51	2
52	1
53	53
54	1
55	4
56	1
57	2
58	1
59	59
60	1
61	61
62	1
63	2
64	1
65	4
66	1
67	67
68	1
69	2
70	1
71	71
72	1
73	73
74	1
75	2
76	1
77	6
78	1
79	79
80	1
81	2
82	1
83	83
84	1
85	4
86	1
87	2
88	1
89	89

[0, 2, 3, 1, 5, 1, 7, 1, 2, 1, 11, 1, 13, 1, 2, 1, 17, 1, 19, 1, 2, 1, 23, 1, 4, 1, 2, 1, 29, 1, 31, 1, 2, 1, 4, 1, 37, 1, 2, 1, 41, 1, 43, 1, 2, 1, 47, 1, 6, 1, 2, 1, 53, 1, 4, 1, 2, 1, 59, 1, 61, 1, 2, 1, 4, 1, 67, 1, 2, 1, 71, 1, 73, 1, 2, 1, 6, 1, 79, 1, 2, 1, 83, 1, 4, 1, 2, 1, 89]

cp's OEIS Frontend

A250480 a(1) = 0, and for n > 1: if n is a prime, a(n) = n, otherwise a(n) = A020639(n) - 1, where A020639(n) gives the least prime dividing n.

Table of values

List of values

n	a(n)
1	0
2	2
3	3
4	1
5	5
6	1
7	7
8	1
9	2
10	1
11	11
12	1
13	13
14	1
15	2
16	1
17	17
18	1
19	19
20	1
21	2
22	1
23	23
24	1
25	4
26	1
27	2
28	1
29	29
30	1
31	31
32	1
33	2
34	1
35	4
36	1
37	37
38	1
39	2
40	1
41	41
42	1
43	43
44	1
45	2
46	1
47	47
48	1
49	6
50	1
51	2
52	1
53	53
54	1
55	4
56	1
57	2
58	1
59	59
60	1
61	61
62	1
63	2
64	1
65	4
66	1
67	67
68	1
69	2
70	1
71	71
72	1
73	73
74	1
75	2
76	1
77	6
78	1
79	79
80	1
81	2
82	1
83	83
84	1
85	4
86	1
87	2
88	1
89	89

n	a(n)
1	0
2	2
3	3
4	1
5	5
6	1
7	7
8	1
9	2
10	1
11	11
12	1
13	13
14	1
15	2
16	1
17	17
18	1
19	19
20	1
21	2
22	1
23	23
24	1
25	4
26	1
27	2
28	1
29	29
30	1
31	31
32	1
33	2
34	1
35	4
36	1
37	37
38	1
39	2
40	1
41	41
42	1
43	43
44	1
45	2
46	1
47	47
48	1
49	6
50	1
51	2
52	1
53	53
54	1
55	4
56	1
57	2
58	1
59	59
60	1
61	61
62	1
63	2
64	1
65	4
66	1
67	67
68	1
69	2
70	1
71	71
72	1
73	73
74	1
75	2
76	1
77	6
78	1
79	79
80	1
81	2
82	1
83	83
84	1
85	4
86	1
87	2
88	1
89	89

n	a(n)
1	0
2	2
3	3
4	1
5	5
6	1
7	7
8	1
9	2
10	1
11	11
12	1
13	13
14	1
15	2
16	1
17	17
18	1
19	19
20	1
21	2
22	1
23	23
24	1
25	4
26	1
27	2
28	1
29	29
30	1
31	31
32	1
33	2
34	1
35	4
36	1
37	37
38	1
39	2
40	1
41	41
42	1
43	43
44	1
45	2
46	1
47	47
48	1
49	6
50	1
51	2
52	1
53	53
54	1
55	4
56	1
57	2
58	1
59	59
60	1
61	61
62	1
63	2
64	1
65	4
66	1
67	67
68	1
69	2
70	1
71	71
72	1
73	73
74	1
75	2
76	1
77	6
78	1
79	79
80	1
81	2
82	1
83	83
84	1
85	4
86	1
87	2
88	1
89	89