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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.

A320346 a(n) is the number of perfect matchings in the graph with vertices labeled 1 to 2n with edges {i,j} for 1<=|i-j|<=4.

Table of values

n a(n)
0 1
1 1
2 3
3 12
4 35
5 105
6 329
7 1014
8 3116
9 9610
10 29625
11 91279
12 281303
13 866948
14 2671727
15 8233671
16 25374513
17 78198928
18 240992592
19 742688720
20 2288811009
21 7053635369
22 21737825143
23 66991419284
24 206453506615
25 636246416105
26 1960778041673
27 6042706771910
28 18622355183932
29 57390193784986
30 176864543185497

List of values

[1, 1, 3, 12, 35, 105, 329, 1014, 3116, 9610, 29625, 91279, 281303, 866948, 2671727, 8233671, 25374513, 78198928, 240992592, 742688720, 2288811009, 7053635369, 21737825143, 66991419284, 206453506615, 636246416105, 1960778041673, 6042706771910, 18622355183932, 57390193784986, 176864543185497]

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

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