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.

A190825 Number of permutations of 2 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 4.

Table of values

n a(n)
0 1
1 0
2 0
3 0
4 0
5 1
6 40
7 876
8 16924
9 332507
10 6944594
11 156127796
12 3783620060
13 98614428186
14 2754950165519
15 82200735013648
16 2610496155216456
17 87952061484214504
18 3134296573781405311
19 117816169705165137052
20 4659486136831587519216
21 193431371632142599974128

List of values

[1, 0, 0, 0, 0, 1, 40, 876, 16924, 332507, 6944594, 156127796, 3783620060, 98614428186, 2754950165519, 82200735013648, 2610496155216456, 87952061484214504, 3134296573781405311, 117816169705165137052, 4659486136831587519216, 193431371632142599974128]

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

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