A365521 - cp's OEIS frontend

A365521 a(1) = 1; for n > 1, a(n) is the prime factor of n that has not appeared for the longest time in {a(1),...,a(n-2),a(n-1)}.

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

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

cp's OEIS Frontend

A365521 a(1) = 1; for n > 1, a(n) is the prime factor of n that has not appeared for the longest time in {a(1),...,a(n-2),a(n-1)}.

Table of values

List of values

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

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

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