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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.

A027289 a(n) = Sum_{k=0..floor(n/2)-1} T(n,k) * T(n,k+2), with T given by A026009.

Table of values

n a(n)
2 1
3 3
4 18
5 55
6 264
7 847
8 3744
9 12465
10 52868
11 180895
12 749220
13 2617173
14 10680656
15 37915317
16 153240864
17 551019963
18 2212417314
19 8038946075
20 32129224712
21 117758845827
22 469105048654
23 1731917060158
24 6882935960496
25 25569740611270
26 101442831429264
27 378875492015643

List of values

[1, 3, 18, 55, 264, 847, 3744, 12465, 52868, 180895, 749220, 2617173, 10680656, 37915317, 153240864, 551019963, 2212417314, 8038946075, 32129224712, 117758845827, 469105048654, 1731917060158, 6882935960496, 25569740611270, 101442831429264, 378875492015643]

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

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