A245359 - cp's OEIS frontend

A245359 Largest number k such that d_1^j + d_2^j + … + d_r^j is prime for all j = 1, 2, .. k, or 0 if no such k exists, where d_1, d_2, … d_r are the digits of n. a(n) = -1 if k is infinite.

n	a(n)
1	0
2	1
3	1
4	0
5	1
6	0
7	1
8	0
9	0
10	0
11	-1
12	2
13	0
14	2
15	0
16	2
17	0
18	0
19	0
20	1
21	2
22	0
23	2
24	0
25	2
26	0
27	0
28	0
29	1
30	1
31	0
32	2
33	0
34	1
35	0
36	0
37	0
38	2
39	0
40	0
41	2
42	0
43	1
44	0
45	0
46	0
47	1
48	0
49	2
50	1
51	0
52	2
53	0
54	0
55	0
56	2
57	0
58	2
59	0
60	0
61	2
62	0
63	0
64	0
65	2
66	0
67	1
68	0
69	0
70	1
71	0
72	0
73	0
74	1
75	0
76	1
77	0
78	0
79	0
80	0
81	0
82	0
83	2
84	0
85	2
86	0
87	0
88	0
89	1
90	0
91	0
92	1
93	0
94	2

[0, 1, 1, 0, 1, 0, 1, 0, 0, 0, -1, 2, 0, 2, 0, 2, 0, 0, 0, 1, 2, 0, 2, 0, 2, 0, 0, 0, 1, 1, 0, 2, 0, 1, 0, 0, 0, 2, 0, 0, 2, 0, 1, 0, 0, 0, 1, 0, 2, 1, 0, 2, 0, 0, 0, 2, 0, 2, 0, 0, 2, 0, 0, 0, 2, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0, 1, 0, 0, 1, 0, 2]

cp's OEIS Frontend

A245359 Largest number k such that d_1^j + d_2^j + … + d_r^j is prime for all j = 1, 2, .. k, or 0 if no such k exists, where d_1, d_2, … d_r are the digits of n. a(n) = -1 if k is infinite.

Table of values

List of values

n	a(n)
1	0
2	1
3	1
4	0
5	1
6	0
7	1
8	0
9	0
10	0
11	-1
12	2
13	0
14	2
15	0
16	2
17	0
18	0
19	0
20	1
21	2
22	0
23	2
24	0
25	2
26	0
27	0
28	0
29	1
30	1
31	0
32	2
33	0
34	1
35	0
36	0
37	0
38	2
39	0
40	0
41	2
42	0
43	1
44	0
45	0
46	0
47	1
48	0
49	2
50	1
51	0
52	2
53	0
54	0
55	0
56	2
57	0
58	2
59	0
60	0
61	2
62	0
63	0
64	0
65	2
66	0
67	1
68	0
69	0
70	1
71	0
72	0
73	0
74	1
75	0
76	1
77	0
78	0
79	0
80	0
81	0
82	0
83	2
84	0
85	2
86	0
87	0
88	0
89	1
90	0
91	0
92	1
93	0
94	2

n	a(n)
1	0
2	1
3	1
4	0
5	1
6	0
7	1
8	0
9	0
10	0
11	-1
12	2
13	0
14	2
15	0
16	2
17	0
18	0
19	0
20	1
21	2
22	0
23	2
24	0
25	2
26	0
27	0
28	0
29	1
30	1
31	0
32	2
33	0
34	1
35	0
36	0
37	0
38	2
39	0
40	0
41	2
42	0
43	1
44	0
45	0
46	0
47	1
48	0
49	2
50	1
51	0
52	2
53	0
54	0
55	0
56	2
57	0
58	2
59	0
60	0
61	2
62	0
63	0
64	0
65	2
66	0
67	1
68	0
69	0
70	1
71	0
72	0
73	0
74	1
75	0
76	1
77	0
78	0
79	0
80	0
81	0
82	0
83	2
84	0
85	2
86	0
87	0
88	0
89	1
90	0
91	0
92	1
93	0
94	2

n	a(n)
1	0
2	1
3	1
4	0
5	1
6	0
7	1
8	0
9	0
10	0
11	-1
12	2
13	0
14	2
15	0
16	2
17	0
18	0
19	0
20	1
21	2
22	0
23	2
24	0
25	2
26	0
27	0
28	0
29	1
30	1
31	0
32	2
33	0
34	1
35	0
36	0
37	0
38	2
39	0
40	0
41	2
42	0
43	1
44	0
45	0
46	0
47	1
48	0
49	2
50	1
51	0
52	2
53	0
54	0
55	0
56	2
57	0
58	2
59	0
60	0
61	2
62	0
63	0
64	0
65	2
66	0
67	1
68	0
69	0
70	1
71	0
72	0
73	0
74	1
75	0
76	1
77	0
78	0
79	0
80	0
81	0
82	0
83	2
84	0
85	2
86	0
87	0
88	0
89	1
90	0
91	0
92	1
93	0
94	2