A125887 - cp's OEIS frontend

A125887 a(1) = 1, a(n) = smallest positive number b not among a(1)..a(n-1) and not a multiple of 10 such that the first digit of b = the last digit of a(n-1).

n	a(n)
1	1
2	11
3	12
4	21
5	13
6	31
7	14
8	41
9	15
10	51
11	16
12	61
13	17
14	71
15	18
16	81
17	19
18	91
19	101
20	102
21	22
22	23
23	32
24	24
25	42
26	25
27	52
28	26
29	62
30	27
31	72
32	28
33	82
34	29
35	92
36	201
37	103
38	33
39	34
40	43
41	35
42	53
43	36
44	63
45	37
46	73
47	38
48	83
49	39
50	93
51	301
52	104
53	44
54	45
55	54
56	46
57	64
58	47
59	74
60	48
61	84
62	49
63	94
64	401
65	105
66	55
67	56
68	65

[1, 11, 12, 21, 13, 31, 14, 41, 15, 51, 16, 61, 17, 71, 18, 81, 19, 91, 101, 102, 22, 23, 32, 24, 42, 25, 52, 26, 62, 27, 72, 28, 82, 29, 92, 201, 103, 33, 34, 43, 35, 53, 36, 63, 37, 73, 38, 83, 39, 93, 301, 104, 44, 45, 54, 46, 64, 47, 74, 48, 84, 49, 94, 401, 105, 55, 56, 65]

cp's OEIS Frontend

A125887 a(1) = 1, a(n) = smallest positive number b not among a(1)..a(n-1) and not a multiple of 10 such that the first digit of b = the last digit of a(n-1).

Table of values

List of values

n	a(n)
1	1
2	11
3	12
4	21
5	13
6	31
7	14
8	41
9	15
10	51
11	16
12	61
13	17
14	71
15	18
16	81
17	19
18	91
19	101
20	102
21	22
22	23
23	32
24	24
25	42
26	25
27	52
28	26
29	62
30	27
31	72
32	28
33	82
34	29
35	92
36	201
37	103
38	33
39	34
40	43
41	35
42	53
43	36
44	63
45	37
46	73
47	38
48	83
49	39
50	93
51	301
52	104
53	44
54	45
55	54
56	46
57	64
58	47
59	74
60	48
61	84
62	49
63	94
64	401
65	105
66	55
67	56
68	65

n	a(n)
1	1
2	11
3	12
4	21
5	13
6	31
7	14
8	41
9	15
10	51
11	16
12	61
13	17
14	71
15	18
16	81
17	19
18	91
19	101
20	102
21	22
22	23
23	32
24	24
25	42
26	25
27	52
28	26
29	62
30	27
31	72
32	28
33	82
34	29
35	92
36	201
37	103
38	33
39	34
40	43
41	35
42	53
43	36
44	63
45	37
46	73
47	38
48	83
49	39
50	93
51	301
52	104
53	44
54	45
55	54
56	46
57	64
58	47
59	74
60	48
61	84
62	49
63	94
64	401
65	105
66	55
67	56
68	65

n	a(n)
1	1
2	11
3	12
4	21
5	13
6	31
7	14
8	41
9	15
10	51
11	16
12	61
13	17
14	71
15	18
16	81
17	19
18	91
19	101
20	102
21	22
22	23
23	32
24	24
25	42
26	25
27	52
28	26
29	62
30	27
31	72
32	28
33	82
34	29
35	92
36	201
37	103
38	33
39	34
40	43
41	35
42	53
43	36
44	63
45	37
46	73
47	38
48	83
49	39
50	93
51	301
52	104
53	44
54	45
55	54
56	46
57	64
58	47
59	74
60	48
61	84
62	49
63	94
64	401
65	105
66	55
67	56
68	65