A000720 - OEIS

A000720 as a simple table

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

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

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

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

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