cp's OEIS Frontend

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.

A115112 Number of different ways to select n elements from two sets of n elements under the precondition of choosing at least one element from each set.

Table of values

n a(n)
1 0
2 4
3 18
4 68
5 250
6 922
7 3430
8 12868
9 48618
10 184754
11 705430
12 2704154
13 10400598
14 40116598
15 155117518
16 601080388
17 2333606218
18 9075135298
19 35345263798
20 137846528818
21 538257874438
22 2104098963718
23 8233430727598
24 32247603683098
25 126410606437750
26 495918532948102

List of values

[0, 4, 18, 68, 250, 922, 3430, 12868, 48618, 184754, 705430, 2704154, 10400598, 40116598, 155117518, 601080388, 2333606218, 9075135298, 35345263798, 137846528818, 538257874438, 2104098963718, 8233430727598, 32247603683098, 126410606437750, 495918532948102]

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

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