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.

A188494 Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i and p(1) <= 2.

Table of values

n a(n)
0 0
1 1
2 2
3 4
4 12
5 42
6 138
7 414
8 1235
9 3764
10 11604
11 35664
12 109132
13 333652
14 1021220
15 3127709
16 9578526
17 29326904
18 89785684
19 274896606
20 841682902
21 2577075290
22 7890425175
23 24158602552
24 73968049928
25 226473538032
26 693411153800
27 2123068036904
28 6500352097064

List of values

[0, 1, 2, 4, 12, 42, 138, 414, 1235, 3764, 11604, 35664, 109132, 333652, 1021220, 3127709, 9578526, 29326904, 89785684, 274896606, 841682902, 2577075290, 7890425175, 24158602552, 73968049928, 226473538032, 693411153800, 2123068036904, 6500352097064]

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

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