A020639 - cp's OEIS frontend

A020639 Lpf(n): least prime dividing n (when n > 1); a(1) = 1. Or, smallest prime factor of n, or smallest prime divisor of n.

n	a(n)
1	1
2	2
3	3
4	2
5	5
6	2
7	7
8	2
9	3
10	2
11	11
12	2
13	13
14	2
15	3
16	2
17	17
18	2
19	19
20	2
21	3
22	2
23	23
24	2
25	5
26	2
27	3
28	2
29	29
30	2
31	31
32	2
33	3
34	2
35	5
36	2
37	37
38	2
39	3
40	2
41	41
42	2
43	43
44	2
45	3
46	2
47	47
48	2
49	7
50	2
51	3
52	2
53	53
54	2
55	5
56	2
57	3
58	2
59	59
60	2
61	61
62	2
63	3
64	2
65	5
66	2
67	67
68	2
69	3
70	2
71	71
72	2
73	73
74	2
75	3
76	2
77	7
78	2
79	79
80	2
81	3
82	2
83	83
84	2
85	5
86	2
87	3
88	2
89	89
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	97

[1, 2, 3, 2, 5, 2, 7, 2, 3, 2, 11, 2, 13, 2, 3, 2, 17, 2, 19, 2, 3, 2, 23, 2, 5, 2, 3, 2, 29, 2, 31, 2, 3, 2, 5, 2, 37, 2, 3, 2, 41, 2, 43, 2, 3, 2, 47, 2, 7, 2, 3, 2, 53, 2, 5, 2, 3, 2, 59, 2, 61, 2, 3, 2, 5, 2, 67, 2, 3, 2, 71, 2, 73, 2, 3, 2, 7, 2, 79, 2, 3, 2, 83, 2, 5, 2, 3, 2, 89, 2, 7, 2, 3, 2, 5, 2, 97]

cp's OEIS Frontend

A020639 Lpf(n): least prime dividing n (when n > 1); a(1) = 1. Or, smallest prime factor of n, or smallest prime divisor of n.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	2
5	5
6	2
7	7
8	2
9	3
10	2
11	11
12	2
13	13
14	2
15	3
16	2
17	17
18	2
19	19
20	2
21	3
22	2
23	23
24	2
25	5
26	2
27	3
28	2
29	29
30	2
31	31
32	2
33	3
34	2
35	5
36	2
37	37
38	2
39	3
40	2
41	41
42	2
43	43
44	2
45	3
46	2
47	47
48	2
49	7
50	2
51	3
52	2
53	53
54	2
55	5
56	2
57	3
58	2
59	59
60	2
61	61
62	2
63	3
64	2
65	5
66	2
67	67
68	2
69	3
70	2
71	71
72	2
73	73
74	2
75	3
76	2
77	7
78	2
79	79
80	2
81	3
82	2
83	83
84	2
85	5
86	2
87	3
88	2
89	89
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	97

n	a(n)
1	1
2	2
3	3
4	2
5	5
6	2
7	7
8	2
9	3
10	2
11	11
12	2
13	13
14	2
15	3
16	2
17	17
18	2
19	19
20	2
21	3
22	2
23	23
24	2
25	5
26	2
27	3
28	2
29	29
30	2
31	31
32	2
33	3
34	2
35	5
36	2
37	37
38	2
39	3
40	2
41	41
42	2
43	43
44	2
45	3
46	2
47	47
48	2
49	7
50	2
51	3
52	2
53	53
54	2
55	5
56	2
57	3
58	2
59	59
60	2
61	61
62	2
63	3
64	2
65	5
66	2
67	67
68	2
69	3
70	2
71	71
72	2
73	73
74	2
75	3
76	2
77	7
78	2
79	79
80	2
81	3
82	2
83	83
84	2
85	5
86	2
87	3
88	2
89	89
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	97

n	a(n)
1	1
2	2
3	3
4	2
5	5
6	2
7	7
8	2
9	3
10	2
11	11
12	2
13	13
14	2
15	3
16	2
17	17
18	2
19	19
20	2
21	3
22	2
23	23
24	2
25	5
26	2
27	3
28	2
29	29
30	2
31	31
32	2
33	3
34	2
35	5
36	2
37	37
38	2
39	3
40	2
41	41
42	2
43	43
44	2
45	3
46	2
47	47
48	2
49	7
50	2
51	3
52	2
53	53
54	2
55	5
56	2
57	3
58	2
59	59
60	2
61	61
62	2
63	3
64	2
65	5
66	2
67	67
68	2
69	3
70	2
71	71
72	2
73	73
74	2
75	3
76	2
77	7
78	2
79	79
80	2
81	3
82	2
83	83
84	2
85	5
86	2
87	3
88	2
89	89
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	97