A103935 - cp's OEIS frontend

A103935 Choose a(n) to be the smallest odd number not yet used such that: a(1) = 1, a(2n) = composite, a(2n+1) = prime and partial sums are alternately composite or prime.

n	a(n)
1	1
2	9
3	3
4	15
5	13
6	21
7	5
8	25
9	11
10	27
11	7
12	33
13	23
14	35
15	29
16	39
17	17
18	45
19	31
20	49
21	19
22	51
23	61
24	55
25	37
26	57
27	43
28	63
29	53
30	65
31	41
32	69
33	71
34	75
35	79
36	77
37	73
38	81
39	59
40	85
41	47
42	87
43	103
44	91
45	83
46	93
47	113
48	95
49	109
50	99
51	127
52	105
53	149
54	111
55	139
56	115
57	89
58	117
59	107
60	119
61	97
62	121
63	131
64	123
65	67
66	125

[1, 9, 3, 15, 13, 21, 5, 25, 11, 27, 7, 33, 23, 35, 29, 39, 17, 45, 31, 49, 19, 51, 61, 55, 37, 57, 43, 63, 53, 65, 41, 69, 71, 75, 79, 77, 73, 81, 59, 85, 47, 87, 103, 91, 83, 93, 113, 95, 109, 99, 127, 105, 149, 111, 139, 115, 89, 117, 107, 119, 97, 121, 131, 123, 67, 125]

cp's OEIS Frontend

A103935 Choose a(n) to be the smallest odd number not yet used such that: a(1) = 1, a(2n) = composite, a(2n+1) = prime and partial sums are alternately composite or prime.

Table of values

List of values

n	a(n)
1	1
2	9
3	3
4	15
5	13
6	21
7	5
8	25
9	11
10	27
11	7
12	33
13	23
14	35
15	29
16	39
17	17
18	45
19	31
20	49
21	19
22	51
23	61
24	55
25	37
26	57
27	43
28	63
29	53
30	65
31	41
32	69
33	71
34	75
35	79
36	77
37	73
38	81
39	59
40	85
41	47
42	87
43	103
44	91
45	83
46	93
47	113
48	95
49	109
50	99
51	127
52	105
53	149
54	111
55	139
56	115
57	89
58	117
59	107
60	119
61	97
62	121
63	131
64	123
65	67
66	125

n	a(n)
1	1
2	9
3	3
4	15
5	13
6	21
7	5
8	25
9	11
10	27
11	7
12	33
13	23
14	35
15	29
16	39
17	17
18	45
19	31
20	49
21	19
22	51
23	61
24	55
25	37
26	57
27	43
28	63
29	53
30	65
31	41
32	69
33	71
34	75
35	79
36	77
37	73
38	81
39	59
40	85
41	47
42	87
43	103
44	91
45	83
46	93
47	113
48	95
49	109
50	99
51	127
52	105
53	149
54	111
55	139
56	115
57	89
58	117
59	107
60	119
61	97
62	121
63	131
64	123
65	67
66	125

n	a(n)
1	1
2	9
3	3
4	15
5	13
6	21
7	5
8	25
9	11
10	27
11	7
12	33
13	23
14	35
15	29
16	39
17	17
18	45
19	31
20	49
21	19
22	51
23	61
24	55
25	37
26	57
27	43
28	63
29	53
30	65
31	41
32	69
33	71
34	75
35	79
36	77
37	73
38	81
39	59
40	85
41	47
42	87
43	103
44	91
45	83
46	93
47	113
48	95
49	109
50	99
51	127
52	105
53	149
54	111
55	139
56	115
57	89
58	117
59	107
60	119
61	97
62	121
63	131
64	123
65	67
66	125