A341541 - cp's OEIS frontend

A341541 a(n) is the number of steps to reach square 1 for a walk starting from square n along the shortest path on the square spiral board without stepping on any prime number. a(n) = -1 if such a path does not exist.

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

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

cp's OEIS Frontend

A341541 a(n) is the number of steps to reach square 1 for a walk starting from square n along the shortest path on the square spiral board without stepping on any prime number. a(n) = -1 if such a path does not exist.

Table of values

List of values

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

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

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