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.

A188495 Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i, p(1) <= 2, and p(4) >= 2.

Table of values

n a(n)
0 0
1 1
2 2
3 4
4 10
5 36
6 120
7 368
8 1089
9 3304
10 10168
11 31312
12 95880
13 293120
14 896824
15 2746569
16 8411818
17 25756220
18 78853410
19 241421436
20 739183568
21 2263249600
22 6929580817
23 21216729488
24 64960656448
25 198894856144
26 608971496032
27 1864533223584
28 5708777321872

List of values

[0, 1, 2, 4, 10, 36, 120, 368, 1089, 3304, 10168, 31312, 95880, 293120, 896824, 2746569, 8411818, 25756220, 78853410, 241421436, 739183568, 2263249600, 6929580817, 21216729488, 64960656448, 198894856144, 608971496032, 1864533223584, 5708777321872]

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

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