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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.

A123813 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 8 which 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 1
3 9
4 13
5 153
6 249
7 3011
8 5209
9 63991
10 114321
11 1421173
12 2603433
13 32518012
14 60650817
15 760402013
16 1437977218

List of values

[1, 1, 9, 13, 153, 249, 3011, 5209, 63991, 114321, 1421173, 2603433, 32518012, 60650817, 760402013, 1437977218]

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

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