A276781 - cp's OEIS frontend

A276781 a(n) = 1+n-(nearest power of prime <= n); for n > 1, a(n) = minimal b such that the numbers binomial(n,k) for b <= k <= n-b have a common divisor greater than 1.

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

[1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 3, 1, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 2, 3, 4, 5, 1, 2, 3, 4, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 3, 4, 1, 2, 3, 4, 5, 6, 1, 2, 1, 2, 3, 1, 2, 3, 1, 2, 3, 4, 1, 2, 1, 2, 3, 4, 5, 6, 1, 2, 1, 2, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 1, 2]

cp's OEIS Frontend

A276781 a(n) = 1+n-(nearest power of prime <= n); for n > 1, a(n) = minimal b such that the numbers binomial(n,k) for b <= k <= n-b have a common divisor greater than 1.

Table of values

List of values

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

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

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