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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.

A084615 a(n) = sum of absolute values of coefficients of (1+x-3x^2)^n.

Table of values

n a(n)
0 1
1 5
2 23
3 99
4 401
5 1525
6 6345
7 27331
8 122083
9 520805
10 2117293
11 8301441
12 34517395
13 147850771
14 628707981
15 2675100397
16 10920387779
17 43701876543
18 180872758207
19 769658883325
20 3243501133481
21 13617178197183
22 56148348498199

List of values

[1, 5, 23, 99, 401, 1525, 6345, 27331, 122083, 520805, 2117293, 8301441, 34517395, 147850771, 628707981, 2675100397, 10920387779, 43701876543, 180872758207, 769658883325, 3243501133481, 13617178197183, 56148348498199]

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

Content is available under The OEIS End-User License Agreement.