A063918 - cp's OEIS frontend

A063918 a(1) = 1 and - applying the sieve of Eratosthenes - for n > 1: a(n) = if n is prime then 0 else the first prime p which marks n as composite.

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	2
7	0
8	2
9	3
10	2
11	0
12	2
13	0
14	2
15	3
16	2
17	0
18	2
19	0
20	2
21	3
22	2
23	0
24	2
25	5
26	2
27	3
28	2
29	0
30	2
31	0
32	2
33	3
34	2
35	5
36	2
37	0
38	2
39	3
40	2
41	0
42	2
43	0
44	2
45	3
46	2
47	0
48	2
49	7
50	2
51	3
52	2
53	0
54	2
55	5
56	2
57	3
58	2
59	0
60	2
61	0
62	2
63	3
64	2
65	5
66	2
67	0
68	2
69	3
70	2
71	0
72	2
73	0
74	2
75	3
76	2
77	7
78	2
79	0
80	2
81	3
82	2
83	0
84	2
85	5
86	2
87	3
88	2
89	0
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	0
98	2
99	3
100	2
101	0
102	2
103	0
104	2
105	3

[1, 0, 0, 2, 0, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 5, 2, 3, 2, 0, 2, 0, 2, 3, 2, 5, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 7, 2, 3, 2, 0, 2, 5, 2, 3, 2, 0, 2, 0, 2, 3, 2, 5, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 7, 2, 0, 2, 3, 2, 0, 2, 5, 2, 3, 2, 0, 2, 7, 2, 3, 2, 5, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3]

cp's OEIS Frontend

A063918 a(1) = 1 and - applying the sieve of Eratosthenes - for n > 1: a(n) = if n is prime then 0 else the first prime p which marks n as composite.

Table of values

List of values

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	2
7	0
8	2
9	3
10	2
11	0
12	2
13	0
14	2
15	3
16	2
17	0
18	2
19	0
20	2
21	3
22	2
23	0
24	2
25	5
26	2
27	3
28	2
29	0
30	2
31	0
32	2
33	3
34	2
35	5
36	2
37	0
38	2
39	3
40	2
41	0
42	2
43	0
44	2
45	3
46	2
47	0
48	2
49	7
50	2
51	3
52	2
53	0
54	2
55	5
56	2
57	3
58	2
59	0
60	2
61	0
62	2
63	3
64	2
65	5
66	2
67	0
68	2
69	3
70	2
71	0
72	2
73	0
74	2
75	3
76	2
77	7
78	2
79	0
80	2
81	3
82	2
83	0
84	2
85	5
86	2
87	3
88	2
89	0
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	0
98	2
99	3
100	2
101	0
102	2
103	0
104	2
105	3

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	2
7	0
8	2
9	3
10	2
11	0
12	2
13	0
14	2
15	3
16	2
17	0
18	2
19	0
20	2
21	3
22	2
23	0
24	2
25	5
26	2
27	3
28	2
29	0
30	2
31	0
32	2
33	3
34	2
35	5
36	2
37	0
38	2
39	3
40	2
41	0
42	2
43	0
44	2
45	3
46	2
47	0
48	2
49	7
50	2
51	3
52	2
53	0
54	2
55	5
56	2
57	3
58	2
59	0
60	2
61	0
62	2
63	3
64	2
65	5
66	2
67	0
68	2
69	3
70	2
71	0
72	2
73	0
74	2
75	3
76	2
77	7
78	2
79	0
80	2
81	3
82	2
83	0
84	2
85	5
86	2
87	3
88	2
89	0
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	0
98	2
99	3
100	2
101	0
102	2
103	0
104	2
105	3

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	2
7	0
8	2
9	3
10	2
11	0
12	2
13	0
14	2
15	3
16	2
17	0
18	2
19	0
20	2
21	3
22	2
23	0
24	2
25	5
26	2
27	3
28	2
29	0
30	2
31	0
32	2
33	3
34	2
35	5
36	2
37	0
38	2
39	3
40	2
41	0
42	2
43	0
44	2
45	3
46	2
47	0
48	2
49	7
50	2
51	3
52	2
53	0
54	2
55	5
56	2
57	3
58	2
59	0
60	2
61	0
62	2
63	3
64	2
65	5
66	2
67	0
68	2
69	3
70	2
71	0
72	2
73	0
74	2
75	3
76	2
77	7
78	2
79	0
80	2
81	3
82	2
83	0
84	2
85	5
86	2
87	3
88	2
89	0
90	2
91	7
92	2
93	3
94	2
95	5
96	2
97	0
98	2
99	3
100	2
101	0
102	2
103	0
104	2
105	3