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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.

A027288 a(n) = Sum_{k=0..floor(n/2)} T(n,k) * T(n,k+1), with T given by A026009.

Table of values

n a(n)
0 1
1 4
2 12
3 46
4 145
5 552
6 1820
7 6918
8 23562
9 89645
10 312664
11 1191885
12 4232345
13 16170728
14 58229100
15 222997812
16 811985790
17 3116622123
18 11451785640
19 44047806725
20 163072988442
21 628465576101
22 2341484487832
23 9040083756276
24 33863310322100
25 130957152428622

List of values

[1, 4, 12, 46, 145, 552, 1820, 6918, 23562, 89645, 312664, 1191885, 4232345, 16170728, 58229100, 222997812, 811985790, 3116622123, 11451785640, 44047806725, 163072988442, 628465576101, 2341484487832, 9040083756276, 33863310322100, 130957152428622]

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

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