A175424 - cp's OEIS frontend

A175424 a(n) is the number of steps of iterations of {(((D_k^D_(k-1))^D_(k-2))^...)^D_1, where D_k is the k-th digit D of number r and k is the number of digits of number r in decimal expansion of r (A055642)} needed to reach a single-digit number starting at r = n, or a(n) = -1 if a single-digit number is never reached.

n	a(n)
0	0
1	0
2	0
3	0
4	0
5	0
6	0
7	0
8	0
9	0
10	1
11	1
12	1
13	1
14	1
15	1
16	1
17	1
18	1
19	1
20	1
21	1
22	1
23	1
24	2
25	-1
26	-1
27	3
28	3
29	2
30	1
31	1
32	1
33	4
34	3
35	-1
36	-1
37	3
38	3
39	3
40	1
41	1
42	2
43	2
44	3
45	3
46	3
47	2
48	2
49	2
50	1
51	1
52	2
53	3
54	2
55	4
56	3
57	2
58	3
59	2
60	1
61	1
62	3
63	3
64	2
65	3
66	3
67	3
68	3
69	2
70	1
71	1
72	4
73	3
74	3
75	3
76	3
77	3
78	2
79	3
80	1
81	1
82	3
83	2
84	3
85	2
86	3
87	2
88	2
89	2
90	1
91	1
92	3
93	3
94	3
95	3
96	2
97	2
98	2
99	2

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, -1, -1, 3, 3, 2, 1, 1, 1, 4, 3, -1, -1, 3, 3, 3, 1, 1, 2, 2, 3, 3, 3, 2, 2, 2, 1, 1, 2, 3, 2, 4, 3, 2, 3, 2, 1, 1, 3, 3, 2, 3, 3, 3, 3, 2, 1, 1, 4, 3, 3, 3, 3, 3, 2, 3, 1, 1, 3, 2, 3, 2, 3, 2, 2, 2, 1, 1, 3, 3, 3, 3, 2, 2, 2, 2]

cp's OEIS Frontend

Table of values

List of values

n	a(n)
0	0
1	0
2	0
3	0
4	0
5	0
6	0
7	0
8	0
9	0
10	1
11	1
12	1
13	1
14	1
15	1
16	1
17	1
18	1
19	1
20	1
21	1
22	1
23	1
24	2
25	-1
26	-1
27	3
28	3
29	2
30	1
31	1
32	1
33	4
34	3
35	-1
36	-1
37	3
38	3
39	3
40	1
41	1
42	2
43	2
44	3
45	3
46	3
47	2
48	2
49	2
50	1
51	1
52	2
53	3
54	2
55	4
56	3
57	2
58	3
59	2
60	1
61	1
62	3
63	3
64	2
65	3
66	3
67	3
68	3
69	2
70	1
71	1
72	4
73	3
74	3
75	3
76	3
77	3
78	2
79	3
80	1
81	1
82	3
83	2
84	3
85	2
86	3
87	2
88	2
89	2
90	1
91	1
92	3
93	3
94	3
95	3
96	2
97	2
98	2
99	2

n	a(n)
0	0
1	0
2	0
3	0
4	0
5	0
6	0
7	0
8	0
9	0
10	1
11	1
12	1
13	1
14	1
15	1
16	1
17	1
18	1
19	1
20	1
21	1
22	1
23	1
24	2
25	-1
26	-1
27	3
28	3
29	2
30	1
31	1
32	1
33	4
34	3
35	-1
36	-1
37	3
38	3
39	3
40	1
41	1
42	2
43	2
44	3
45	3
46	3
47	2
48	2
49	2
50	1
51	1
52	2
53	3
54	2
55	4
56	3
57	2
58	3
59	2
60	1
61	1
62	3
63	3
64	2
65	3
66	3
67	3
68	3
69	2
70	1
71	1
72	4
73	3
74	3
75	3
76	3
77	3
78	2
79	3
80	1
81	1
82	3
83	2
84	3
85	2
86	3
87	2
88	2
89	2
90	1
91	1
92	3
93	3
94	3
95	3
96	2
97	2
98	2
99	2

n	a(n)
0	0
1	0
2	0
3	0
4	0
5	0
6	0
7	0
8	0
9	0
10	1
11	1
12	1
13	1
14	1
15	1
16	1
17	1
18	1
19	1
20	1
21	1
22	1
23	1
24	2
25	-1
26	-1
27	3
28	3
29	2
30	1
31	1
32	1
33	4
34	3
35	-1
36	-1
37	3
38	3
39	3
40	1
41	1
42	2
43	2
44	3
45	3
46	3
47	2
48	2
49	2
50	1
51	1
52	2
53	3
54	2
55	4
56	3
57	2
58	3
59	2
60	1
61	1
62	3
63	3
64	2
65	3
66	3
67	3
68	3
69	2
70	1
71	1
72	4
73	3
74	3
75	3
76	3
77	3
78	2
79	3
80	1
81	1
82	3
83	2
84	3
85	2
86	3
87	2
88	2
89	2
90	1
91	1
92	3
93	3
94	3
95	3
96	2
97	2
98	2
99	2