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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.

A123789 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 5 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 5
4 7
5 49
6 77
7 572
8 949
9 7245
10 12361
11 96063
12 167564
13 1313467
14 2327488
15 18365795
16 32936281
17 261111133
18 472694546

List of values

[1, 1, 5, 7, 49, 77, 572, 949, 7245, 12361, 96063, 167564, 1313467, 2327488, 18365795, 32936281, 261111133, 472694546]

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

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