A378680 - cp's OEIS frontend

A378680 a(n) = numerator(Sum_{k=1..n} 1/P_2(k)), where P_2(k) = A087040(k) is the second largest prime dividing the k-th composite number.

n	a(n)
1	1
2	1
3	3
4	11
5	7
6	17
7	10
8	11
9	25
10	9
11	5
12	16
13	35
14	19
15	98
16	211
17	221
18	118
19	41
20	87
21	271
22	143
23	146
24	151
25	317
26	109
27	57
28	176
29	367
30	377
31	196
32	407
33	2879
34	2921
35	997
36	516
37	1583
38	1604
39	3313
40	3383
41	1744
42	593
43	1221
44	3733
45	1919
46	388
47	395
48	811
49	275
50	1389
51	4237
52	2171
53	2192
54	4489

[1, 1, 3, 11, 7, 17, 10, 11, 25, 9, 5, 16, 35, 19, 98, 211, 221, 118, 41, 87, 271, 143, 146, 151, 317, 109, 57, 176, 367, 377, 196, 407, 2879, 2921, 997, 516, 1583, 1604, 3313, 3383, 1744, 593, 1221, 3733, 1919, 388, 395, 811, 275, 1389, 4237, 2171, 2192, 4489]

cp's OEIS Frontend

A378680 a(n) = numerator(Sum_{k=1..n} 1/P_2(k)), where P_2(k) = A087040(k) is the second largest prime dividing the k-th composite number.

Table of values

List of values