A120744 - cp's OEIS frontend

A120744 Least k>0 such that a centered polygonal number nk(k+1)/2+1 is a perfect square; or -1 if no such number exists.

n	a(n)
1	2
2	-1
3	1
4	3
5	2
6	7
7	15
8	1
9	16
10	8
11	14
12	4
13	5
14	15
15	1
16	2
17	5
18	-1
19	6
20	3
21	2
22	39
23	6
24	1
25	21
26	7
27	110
28	3
29	15
30	7
31	15
32	-1
33	2
34	8
35	1
36	4
37	989
38	8
39	14
40	2
41	45
42	15
43	9
44	4
45	5
46	335
47	9
48	1
49	29
50	-1
51	30
52	15
53	10
54	415
55	6
56	2
57	10
58	32
59	54
60	3
61	77
62	55
63	1
64	5
65	2
66	7
67	47750
68	11
69	15
70	23
71	47
72	-1
73	48
74	24
75	16
76	12
77	5
78	8
79	2639
80	1
81	6720
82	704
83	38
84	4
85	2
86	39
87	505
88	3
89	13
90	56
91	9
92	20
93	13
94	1631
95	41

[2, -1, 1, 3, 2, 7, 15, 1, 16, 8, 14, 4, 5, 15, 1, 2, 5, -1, 6, 3, 2, 39, 6, 1, 21, 7, 110, 3, 15, 7, 15, -1, 2, 8, 1, 4, 989, 8, 14, 2, 45, 15, 9, 4, 5, 335, 9, 1, 29, -1, 30, 15, 10, 415, 6, 2, 10, 32, 54, 3, 77, 55, 1, 5, 2, 7, 47750, 11, 15, 23, 47, -1, 48, 24, 16, 12, 5, 8, 2639, 1, 6720, 704, 38, 4, 2, 39, 505, 3, 13, 56, 9, 20, 13, 1631, 41]

cp's OEIS Frontend

A120744 Least k>0 such that a centered polygonal number nk(k+1)/2+1 is a perfect square; or -1 if no such number exists.

Table of values

List of values