Triangular Number 1 - 25

Do you know your triangular numbers up to and including 25? The sequence is T = n(n+1) all divided by 2

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Last updated: September 22, 2021

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First submitted	September 22, 2021
Times taken	19
Average score	92.0%
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When n = ...	T =
1	1
2	3
3	6
4	10
5	15
6	21
7	28
8	36
9	45
10	55
11	66
12	78
13	91

When n = ...	T =
14	105
15	120
16	136
17	153
18	171
19	190
20	210
21	231
22	253
23	276
24	300
25	325

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