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.

A123785 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 4 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 16
5 36
6 124
7 287
8 1043
9 2573
10 9448
11 24161
12 89827
13 235902
14 886047
15 2372494
16 8968829
17 24410414
18 92783928
19 255723571
20 976331352

List of values

[1, 3, 5, 16, 36, 124, 287, 1043, 2573, 9448, 24161, 89827, 235902, 886047, 2372494, 8968829, 24410414, 92783928, 255723571, 976331352]

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

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