A243056 - cp's OEIS frontend

A243056 If n is the i-th prime, p_i = A000040(i), then a(n) = i, otherwise the difference between the indices of the smallest and the largest prime dividing n: for n = p_i * ... * p_k, where p_i <= ... <= p_k, a(n) = (k-i); a(1) = 0 by convention.

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

[0, 1, 2, 0, 3, 1, 4, 0, 0, 2, 5, 1, 6, 3, 1, 0, 7, 1, 8, 2, 2, 4, 9, 1, 0, 5, 0, 3, 10, 2, 11, 0, 3, 6, 1, 1, 12, 7, 4, 2, 13, 3, 14, 4, 1, 8, 15, 1, 0, 2, 5, 5, 16, 1, 2, 3, 6, 9, 17, 2, 18, 10, 2, 0, 3, 4, 19, 6, 7, 3, 20, 1, 21, 11, 1, 7, 1, 5, 22, 2, 0, 12, 23, 3, 4, 13, 8, 4, 24, 2]

cp's OEIS Frontend

A243056 If n is the i-th prime, p_i = A000040(i), then a(n) = i, otherwise the difference between the indices of the smallest and the largest prime dividing n: for n = p_i * ... * p_k, where p_i <= ... <= p_k, a(n) = (k-i); a(1) = 0 by convention.

Table of values

List of values

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

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

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