A387123 - cp's OEIS frontend

A387123 Numbers k such that Sum_{i=1..r} (k-i) and Sum_{i=1..r} (k+i) are both triangular for some r with 1 <= r < k.

n	a(n)
1	2
2	6
3	9
4	21
5	24
6	38
7	50
8	53
9	65
10	77
11	90
12	96
13	104
14	133
15	147
16	195
17	201
18	224
19	247
20	286
21	324
22	377
23	450
24	483
25	553
26	588
27	605
28	614
29	713
30	792
31	901
32	1014
33	1029
34	1043
35	1066
36	1074
37	1155
38	1274
39	1349
40	1575
41	1784
42	1885
43	1920
44	2034
45	2057
46	2109
47	2279
48	2312
49	2342
50	2622

[2, 6, 9, 21, 24, 38, 50, 53, 65, 77, 90, 96, 104, 133, 147, 195, 201, 224, 247, 286, 324, 377, 450, 483, 553, 588, 605, 614, 713, 792, 901, 1014, 1029, 1043, 1066, 1074, 1155, 1274, 1349, 1575, 1784, 1885, 1920, 2034, 2057, 2109, 2279, 2312, 2342, 2622]

cp's OEIS Frontend

A387123 Numbers k such that Sum_{i=1..r} (k-i) and Sum_{i=1..r} (k+i) are both triangular for some r with 1 <= r < k.

Table of values

List of values