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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.

A071983 Square chains: the number of permutations (reversals not counted as different) of the numbers 1 to n such that the sum of any two consecutive numbers is a square.

Table of values

n a(n)
15 1
16 1
17 1
18 0
19 0
20 0
21 0
22 0
23 3
24 0
25 10
26 12
27 35
28 52
29 19
30 20
31 349
32 392
33 669
34 4041
35 17175
36 12960
37 14026
38 11889
39 29123
40 39550
41 219968
42 553694
43 2178103
44 5301127
45 12220138
46 38838893
47 68361609
48 140571720
49 280217025
50 204853870
51 738704986
52 2368147377
53 5511090791
54 9802605881
55 21164463050
56 47746712739
57 68092497615
58 123092214818

List of values

[1, 1, 1, 0, 0, 0, 0, 0, 3, 0, 10, 12, 35, 52, 19, 20, 349, 392, 669, 4041, 17175, 12960, 14026, 11889, 29123, 39550, 219968, 553694, 2178103, 5301127, 12220138, 38838893, 68361609, 140571720, 280217025, 204853870, 738704986, 2368147377, 5511090791, 9802605881, 21164463050, 47746712739, 68092497615, 123092214818]

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

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