A299251 - cp's OEIS frontend

A299251 a(n) = ((Sum_{k=1..floor((n+1)^2/4)} d(k)) - T(n)) / 2, where d(n) = number of divisors of n (A000005) and T(n) = the n-th triangular number (A000217).

n	a(n)
1	0
2	0
3	1
4	2
5	4
6	7
7	11
8	15
9	21
10	28
11	37
12	45
13	55
14	67
15	80
16	95
17	110
18	127
19	146
20	164
21	187
22	209
23	235
24	260
25	286
26	315
27	346
28	380
29	413
30	449
31	485
32	522
33	564
34	605
35	651
36	695
37	743
38	792
39	844
40	898
41	950
42	1006
43	1064
44	1123
45	1185
46	1250
47	1318
48	1384
49	1451
50	1523
51	1596
52	1670
53	1747
54	1828

[0, 0, 1, 2, 4, 7, 11, 15, 21, 28, 37, 45, 55, 67, 80, 95, 110, 127, 146, 164, 187, 209, 235, 260, 286, 315, 346, 380, 413, 449, 485, 522, 564, 605, 651, 695, 743, 792, 844, 898, 950, 1006, 1064, 1123, 1185, 1250, 1318, 1384, 1451, 1523, 1596, 1670, 1747, 1828]

cp's OEIS Frontend

A299251 a(n) = ((Sum_{k=1..floor((n+1)^2/4)} d(k)) - T(n)) / 2, where d(n) = number of divisors of n (A000005) and T(n) = the n-th triangular number (A000217).

Table of values

List of values