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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.

A123817 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 8 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

Table of values

n a(n)
1 1
2 5
3 9
4 51
5 131
6 807
7 2129
8 13967
9 39701
10 265152
11 781478
12 5287858
13 16094282
14 110147280
15 342365511
16 2360643691

List of values

[1, 5, 9, 51, 131, 807, 2129, 13967, 39701, 265152, 781478, 5287858, 16094282, 110147280, 342365511, 2360643691]

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

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