cp's OEIS Frontend

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.

A123793 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 5 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 3
3 5
4 18
5 42
6 170
7 405
8 1769
9 4507
10 20081
11 53008
12 240428
13 652160
14 3002052
15 8299727
16 38570944
17 108387118
18 507729121
19 1444491686
20 6809942459

List of values

[1, 3, 5, 18, 42, 170, 405, 1769, 4507, 20081, 53008, 240428, 652160, 3002052, 8299727, 38570944, 108387118, 507729121, 1444491686, 6809942459]

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

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