A249744 - cp's OEIS frontend

A249744 a(n) = 0 if n is 1 or a prime, otherwise, when n = A020639(n) * A032742(n), a(n) = the largest m < n such that A020639(m) = A020639(n), where A020639(n) and A032742(n) are the smallest prime and the largest proper divisor dividing n.

n	a(n)
1	0
2	0
3	0
4	2
5	0
6	4
7	0
8	6
9	3
10	8
11	0
12	10
13	0
14	12
15	9
16	14
17	0
18	16
19	0
20	18
21	15
22	20
23	0
24	22
25	5
26	24
27	21
28	26
29	0
30	28
31	0
32	30
33	27
34	32
35	25
36	34
37	0
38	36
39	33
40	38
41	0
42	40
43	0
44	42
45	39
46	44
47	0
48	46
49	7
50	48
51	45
52	50
53	0
54	52
55	35
56	54
57	51
58	56
59	0
60	58
61	0
62	60
63	57
64	62
65	55
66	64
67	0
68	66
69	63
70	68
71	0
72	70
73	0
74	72
75	69
76	74
77	49
78	76
79	0
80	78
81	75
82	80
83	0
84	82
85	65
86	84
87	81
88	86
89	0
90	88
91	77
92	90
93	87
94	92
95	85
96	94
97	0
98	96
99	93
100	98
101	0
102	100

[0, 0, 0, 2, 0, 4, 0, 6, 3, 8, 0, 10, 0, 12, 9, 14, 0, 16, 0, 18, 15, 20, 0, 22, 5, 24, 21, 26, 0, 28, 0, 30, 27, 32, 25, 34, 0, 36, 33, 38, 0, 40, 0, 42, 39, 44, 0, 46, 7, 48, 45, 50, 0, 52, 35, 54, 51, 56, 0, 58, 0, 60, 57, 62, 55, 64, 0, 66, 63, 68, 0, 70, 0, 72, 69, 74, 49, 76, 0, 78, 75, 80, 0, 82, 65, 84, 81, 86, 0, 88, 77, 90, 87, 92, 85, 94, 0, 96, 93, 98, 0, 100]

cp's OEIS Frontend

A249744 a(n) = 0 if n is 1 or a prime, otherwise, when n = A020639(n) * A032742(n), a(n) = the largest m < n such that A020639(m) = A020639(n), where A020639(n) and A032742(n) are the smallest prime and the largest proper divisor dividing n.

Table of values

List of values

n	a(n)
1	0
2	0
3	0
4	2
5	0
6	4
7	0
8	6
9	3
10	8
11	0
12	10
13	0
14	12
15	9
16	14
17	0
18	16
19	0
20	18
21	15
22	20
23	0
24	22
25	5
26	24
27	21
28	26
29	0
30	28
31	0
32	30
33	27
34	32
35	25
36	34
37	0
38	36
39	33
40	38
41	0
42	40
43	0
44	42
45	39
46	44
47	0
48	46
49	7
50	48
51	45
52	50
53	0
54	52
55	35
56	54
57	51
58	56
59	0
60	58
61	0
62	60
63	57
64	62
65	55
66	64
67	0
68	66
69	63
70	68
71	0
72	70
73	0
74	72
75	69
76	74
77	49
78	76
79	0
80	78
81	75
82	80
83	0
84	82
85	65
86	84
87	81
88	86
89	0
90	88
91	77
92	90
93	87
94	92
95	85
96	94
97	0
98	96
99	93
100	98
101	0
102	100

n	a(n)
1	0
2	0
3	0
4	2
5	0
6	4
7	0
8	6
9	3
10	8
11	0
12	10
13	0
14	12
15	9
16	14
17	0
18	16
19	0
20	18
21	15
22	20
23	0
24	22
25	5
26	24
27	21
28	26
29	0
30	28
31	0
32	30
33	27
34	32
35	25
36	34
37	0
38	36
39	33
40	38
41	0
42	40
43	0
44	42
45	39
46	44
47	0
48	46
49	7
50	48
51	45
52	50
53	0
54	52
55	35
56	54
57	51
58	56
59	0
60	58
61	0
62	60
63	57
64	62
65	55
66	64
67	0
68	66
69	63
70	68
71	0
72	70
73	0
74	72
75	69
76	74
77	49
78	76
79	0
80	78
81	75
82	80
83	0
84	82
85	65
86	84
87	81
88	86
89	0
90	88
91	77
92	90
93	87
94	92
95	85
96	94
97	0
98	96
99	93
100	98
101	0
102	100

n	a(n)
1	0
2	0
3	0
4	2
5	0
6	4
7	0
8	6
9	3
10	8
11	0
12	10
13	0
14	12
15	9
16	14
17	0
18	16
19	0
20	18
21	15
22	20
23	0
24	22
25	5
26	24
27	21
28	26
29	0
30	28
31	0
32	30
33	27
34	32
35	25
36	34
37	0
38	36
39	33
40	38
41	0
42	40
43	0
44	42
45	39
46	44
47	0
48	46
49	7
50	48
51	45
52	50
53	0
54	52
55	35
56	54
57	51
58	56
59	0
60	58
61	0
62	60
63	57
64	62
65	55
66	64
67	0
68	66
69	63
70	68
71	0
72	70
73	0
74	72
75	69
76	74
77	49
78	76
79	0
80	78
81	75
82	80
83	0
84	82
85	65
86	84
87	81
88	86
89	0
90	88
91	77
92	90
93	87
94	92
95	85
96	94
97	0
98	96
99	93
100	98
101	0
102	100