A007897 - cp's OEIS frontend

A007897 a(n) is multiplicative with a(2) = 1; a(4) = 2; a(2^i) = 2^(i-2)+2 if i>2; a(p^i) = 1+(p-1)*p^(i-1)/2 if prime p>2 and i>0.

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

[1, 1, 2, 2, 3, 2, 4, 4, 4, 3, 6, 4, 7, 4, 6, 6, 9, 4, 10, 6, 8, 6, 12, 8, 11, 7, 10, 8, 15, 6, 16, 10, 12, 9, 12, 8, 19, 10, 14, 12, 21, 8, 22, 12, 12, 12, 24, 12, 22, 11, 18, 14, 27, 10, 18, 16, 20, 15, 30, 12, 31, 16, 16, 18, 21, 12, 34, 18, 24, 12, 36, 16, 37, 19, 22, 20, 24, 14, 40, 18, 28]

cp's OEIS Frontend

A007897 a(n) is multiplicative with a(2) = 1; a(4) = 2; a(2^i) = 2^(i-2)+2 if i>2; a(p^i) = 1+(p-1)*p^(i-1)/2 if prime p>2 and i>0.

Table of values

List of values

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

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

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