GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
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<td
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style="font-weight: bold;">About HAP: Crossed module and third
cohomology<br>
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<h3>Some classical theory</h3>
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<p>The <a href="aboutTwistedCoefficients.html">cohomology</a>
H<sup>n</sup>(G,A) of G with coefficients in a G-module A, together
with the corresponding <a href="aboutCocycles.html">cocycles</a>,
have a useful group-theoretic interpretation for n=2. <br>
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<h3>An example</h3>
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