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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A295290 a(n) is the smallest triangular number t such that t - n is a square, or -1 if no such triangular number exists.

Table of values

n a(n)
0 0
1 1
2 3
3 3
4 -1
5 6
6 6
7 -1
8 -1
9 10
10 10
11 15
12 21
13 -1
14 15
15 15
16 -1
17 21
18 -1
19 28
20 21
21 21
22 -1
23 -1
24 28
25 -1
26 -1
27 28
28 28
29 45
30 55
31 -1
32 36
33 -1
34 -1
35 36
36 36
37 -1
38 -1
39 55
40 -1
41 45
42 78
43 -1
44 45
45 45
46 55
47 -1
48 -1
49 -1
50 66
51 55
52 -1
53 78
54 55
55 55
56 105
57 66
58 -1
59 -1
60 -1
61 -1
62 66
63 -1
64 -1
65 66

List of values

[0, 1, 3, 3, -1, 6, 6, -1, -1, 10, 10, 15, 21, -1, 15, 15, -1, 21, -1, 28, 21, 21, -1, -1, 28, -1, -1, 28, 28, 45, 55, -1, 36, -1, -1, 36, 36, -1, -1, 55, -1, 45, 78, -1, 45, 45, 55, -1, -1, -1, 66, 55, -1, 78, 55, 55, 105, 66, -1, -1, -1, -1, 66, -1, -1, 66]

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