A251718 - cp's OEIS frontend

A251718 a(n) = smallest positive integer k such that both A083221(k, n) and A083221(k+1, n) have at most two prime factors (are primes or semiprimes).

n	a(n)
1	1
2	1
3	1
4	2
5	3
6	2
7	1
8	3
9	4
10	2
11	3
12	4
13	3
14	5
15	2
16	2
17	4
18	3
19	1
20	3
21	2
22	4
23	3
24	2
25	5
26	4
27	2
28	3
29	4
30	2
31	1
32	5
33	6
34	2
35	3
36	2
37	1
38	3
39	6
40	4
41	4
42	4
43	6
44	3
45	4
46	5
47	3
48	6
49	4
50	6
51	2
52	4
53	3
54	4
55	2
56	5
57	8
58	5
59	6
60	3
61	3
62	4
63	4
64	2
65	3
66	2
67	3
68	7
69	6
70	5
71	3
72	4
73	4
74	6
75	2
76	2
77	5
78	7
79	1
80	5
81	5
82	4
83	6
84	2
85	4
86	6
87	5
88	5
89	4
90	2
91	2
92	5
93	3
94	3
95	3
96	4
97	1
98	3
99	5
100	7
101	5
102	4
103	3
104	3
105	5
106	2
107	4
108	5
109	7
110	4
111	7
112	4
113	3
114	7
115	4
116	3
117	2
118	3
119	4
120	2

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

cp's OEIS Frontend

A251718 a(n) = smallest positive integer k such that both A083221(k, n) and A083221(k+1, n) have at most two prime factors (are primes or semiprimes).

Table of values

List of values

n	a(n)
1	1
2	1
3	1
4	2
5	3
6	2
7	1
8	3
9	4
10	2
11	3
12	4
13	3
14	5
15	2
16	2
17	4
18	3
19	1
20	3
21	2
22	4
23	3
24	2
25	5
26	4
27	2
28	3
29	4
30	2
31	1
32	5
33	6
34	2
35	3
36	2
37	1
38	3
39	6
40	4
41	4
42	4
43	6
44	3
45	4
46	5
47	3
48	6
49	4
50	6
51	2
52	4
53	3
54	4
55	2
56	5
57	8
58	5
59	6
60	3
61	3
62	4
63	4
64	2
65	3
66	2
67	3
68	7
69	6
70	5
71	3
72	4
73	4
74	6
75	2
76	2
77	5
78	7
79	1
80	5
81	5
82	4
83	6
84	2
85	4
86	6
87	5
88	5
89	4
90	2
91	2
92	5
93	3
94	3
95	3
96	4
97	1
98	3
99	5
100	7
101	5
102	4
103	3
104	3
105	5
106	2
107	4
108	5
109	7
110	4
111	7
112	4
113	3
114	7
115	4
116	3
117	2
118	3
119	4
120	2

n	a(n)
1	1
2	1
3	1
4	2
5	3
6	2
7	1
8	3
9	4
10	2
11	3
12	4
13	3
14	5
15	2
16	2
17	4
18	3
19	1
20	3
21	2
22	4
23	3
24	2
25	5
26	4
27	2
28	3
29	4
30	2
31	1
32	5
33	6
34	2
35	3
36	2
37	1
38	3
39	6
40	4
41	4
42	4
43	6
44	3
45	4
46	5
47	3
48	6
49	4
50	6
51	2
52	4
53	3
54	4
55	2
56	5
57	8
58	5
59	6
60	3
61	3
62	4
63	4
64	2
65	3
66	2
67	3
68	7
69	6
70	5
71	3
72	4
73	4
74	6
75	2
76	2
77	5
78	7
79	1
80	5
81	5
82	4
83	6
84	2
85	4
86	6
87	5
88	5
89	4
90	2
91	2
92	5
93	3
94	3
95	3
96	4
97	1
98	3
99	5
100	7
101	5
102	4
103	3
104	3
105	5
106	2
107	4
108	5
109	7
110	4
111	7
112	4
113	3
114	7
115	4
116	3
117	2
118	3
119	4
120	2

n	a(n)
1	1
2	1
3	1
4	2
5	3
6	2
7	1
8	3
9	4
10	2
11	3
12	4
13	3
14	5
15	2
16	2
17	4
18	3
19	1
20	3
21	2
22	4
23	3
24	2
25	5
26	4
27	2
28	3
29	4
30	2
31	1
32	5
33	6
34	2
35	3
36	2
37	1
38	3
39	6
40	4
41	4
42	4
43	6
44	3
45	4
46	5
47	3
48	6
49	4
50	6
51	2
52	4
53	3
54	4
55	2
56	5
57	8
58	5
59	6
60	3
61	3
62	4
63	4
64	2
65	3
66	2
67	3
68	7
69	6
70	5
71	3
72	4
73	4
74	6
75	2
76	2
77	5
78	7
79	1
80	5
81	5
82	4
83	6
84	2
85	4
86	6
87	5
88	5
89	4
90	2
91	2
92	5
93	3
94	3
95	3
96	4
97	1
98	3
99	5
100	7
101	5
102	4
103	3
104	3
105	5
106	2
107	4
108	5
109	7
110	4
111	7
112	4
113	3
114	7
115	4
116	3
117	2
118	3
119	4
120	2