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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.

A071930 Number of words of length 2n in the two letters s and t that reduce to the identity 1 by using the relations ssTT=1, ststSS=1 and ststTT=1, where S and T are the inverses of s and t, respectively (i.e., sS=1 and tT=1). The generators s and t and the three stated relations generate the quaternion group Q4.

Table of values

n a(n)
1 0
2 6
3 12
4 72
5 240
6 1056
7 4032
8 16512
9 65280
10 262656
11 1047552
12 4196352
13 16773120
14 67117056
15 268419072
16 1073774592
17 4294901760
18 17180000256
19 68719214592
20 274878431232
21 1099510579200
22 4398048608256
23 17592181850112

List of values

[0, 6, 12, 72, 240, 1056, 4032, 16512, 65280, 262656, 1047552, 4196352, 16773120, 67117056, 268419072, 1073774592, 4294901760, 17180000256, 68719214592, 274878431232, 1099510579200, 4398048608256, 17592181850112]

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

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