A251606 - cp's OEIS frontend

A251606 Let {d(i)}, i=1..q, be the set of the q prime distinct divisors of a number n, and consider the alternating sum s = Sum_{i=1..q} i*((-1)^(i+1))/d(i) and the product p = Product_{i=1..q} d(i) respectively. The sequence lists the composite numbers n such that s = 1/p.

n	a(n)
1	4
2	8
3	9
4	10
5	16
6	20
7	21
8	25
9	27
10	32
11	40
12	49
13	50
14	55
15	63
16	64
17	80
18	81
19	100
20	102
21	121
22	125
23	128
24	147
25	160
26	169
27	189
28	200
29	204
30	243
31	250
32	253
33	256
34	275
35	289
36	306
37	320
38	343
39	361
40	400
41	408
42	441
43	500
44	512
45	529
46	567
47	605
48	612
49	625
50	640
51	729
52	800
53	816
54	841
55	918
56	961

[4, 8, 9, 10, 16, 20, 21, 25, 27, 32, 40, 49, 50, 55, 63, 64, 80, 81, 100, 102, 121, 125, 128, 147, 160, 169, 189, 200, 204, 243, 250, 253, 256, 275, 289, 306, 320, 343, 361, 400, 408, 441, 500, 512, 529, 567, 605, 612, 625, 640, 729, 800, 816, 841, 918, 961]

cp's OEIS Frontend

A251606 Let {d(i)}, i=1..q, be the set of the q prime distinct divisors of a number n, and consider the alternating sum s = Sum_{i=1..q} i*((-1)^(i+1))/d(i) and the product p = Product_{i=1..q} d(i) respectively. The sequence lists the composite numbers n such that s = 1/p.

Table of values

List of values

n	a(n)
1	4
2	8
3	9
4	10
5	16
6	20
7	21
8	25
9	27
10	32
11	40
12	49
13	50
14	55
15	63
16	64
17	80
18	81
19	100
20	102
21	121
22	125
23	128
24	147
25	160
26	169
27	189
28	200
29	204
30	243
31	250
32	253
33	256
34	275
35	289
36	306
37	320
38	343
39	361
40	400
41	408
42	441
43	500
44	512
45	529
46	567
47	605
48	612
49	625
50	640
51	729
52	800
53	816
54	841
55	918
56	961

n	a(n)
1	4
2	8
3	9
4	10
5	16
6	20
7	21
8	25
9	27
10	32
11	40
12	49
13	50
14	55
15	63
16	64
17	80
18	81
19	100
20	102
21	121
22	125
23	128
24	147
25	160
26	169
27	189
28	200
29	204
30	243
31	250
32	253
33	256
34	275
35	289
36	306
37	320
38	343
39	361
40	400
41	408
42	441
43	500
44	512
45	529
46	567
47	605
48	612
49	625
50	640
51	729
52	800
53	816
54	841
55	918
56	961

n	a(n)
1	4
2	8
3	9
4	10
5	16
6	20
7	21
8	25
9	27
10	32
11	40
12	49
13	50
14	55
15	63
16	64
17	80
18	81
19	100
20	102
21	121
22	125
23	128
24	147
25	160
26	169
27	189
28	200
29	204
30	243
31	250
32	253
33	256
34	275
35	289
36	306
37	320
38	343
39	361
40	400
41	408
42	441
43	500
44	512
45	529
46	567
47	605
48	612
49	625
50	640
51	729
52	800
53	816
54	841
55	918
56	961