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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.

A108484 a(n) = Sum_{k=0..floor(n/2)} binomial(2n-2k,2k) * 3^(n-k).

Table of values

n a(n)
0 1
1 1
2 4
3 19
4 55
5 220
6 793
7 2845
8 10480
9 37963
10 138259
11 503608
12 1831969
13 6669865
14 24276892
15 88362451
16 321640831
17 1170726484
18 4261339801
19 15510894949
20 56458080328
21 205502135851
22 748007984827
23 2722677076336
24 9910284168961

List of values

[1, 1, 4, 19, 55, 220, 793, 2845, 10480, 37963, 138259, 503608, 1831969, 6669865, 24276892, 88362451, 321640831, 1170726484, 4261339801, 15510894949, 56458080328, 205502135851, 748007984827, 2722677076336, 9910284168961]

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

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