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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.

A284251 Number of n-element subsets of [2n] whose sum is a triangular number.

Table of values

n a(n)
0 1
1 1
2 2
3 5
4 11
5 35
6 106
7 337
8 1112
9 3741
10 12821
11 44576
12 156862
13 557580
14 1999117
15 7221134
16 26253632
17 95996850
18 352798772
19 1302457652
20 4828002125
21 17962539164
22 67052864821
23 251066424023
24 942692613615
25 3548654963966
26 13390078255129
27 50635057984917

List of values

[1, 1, 2, 5, 11, 35, 106, 337, 1112, 3741, 12821, 44576, 156862, 557580, 1999117, 7221134, 26253632, 95996850, 352798772, 1302457652, 4828002125, 17962539164, 67052864821, 251066424023, 942692613615, 3548654963966, 13390078255129, 50635057984917]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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