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In our research, we need to know that whether every group $G$ of order $2520 = 2^3 \cdot 3^2 \cdot 5 \cdot 7=\frac{7!}{2}$ or $5040 = 2^4 \cdot 3^2 \cdot 5 \cdot 7=7!$ has a proper subgroup non-isomorphic to the following groups \begin{gather*} C_1,\; C_2,\; C_2\times C_2,\; C_2\times C_2\times C_2,\; C_2\times C_2\times C_2\times C_2, \\ C_3,\; C_3\times C_3,\; C_4,\; C_5,\; S_3,\; C_7,\; C_4\times C_2 ,\; D_8,\; Q_8 \end{gather*} (i.e., all groups of orders $\leq 9$ except $C_6$, $C_8$, $C_9$, together with $C_2\times C_2\times C_2\times C_2$).

Note that

  1. the above list of groups contains at least a $p$-group, for all existing primes $p$ (here), up to their powers.

  2. if $G$ is nilpotent, then it is true (because $G$ would contain the subgroup $C_{p_1p_2}$ for all distinct prime divisors $p_1$ and $p_2$ of $|G|$).

  3. from Groups of order $2520$ it seems the answer is positive for $\lvert G\rvert=2520$.

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  • $\begingroup$ Have you tried an argument along similar lines as my MSE answer? $\endgroup$
    – verret
    Commented Sep 15, 2022 at 18:33
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    $\begingroup$ If not, then a Sylow $3$-subgroup would either be normal, or self-normalizing, in which case there would be a normal $3$-complement by Burnside's Transfer Theorem, and the result follows easily in both cases. $\endgroup$
    – Derek Holt
    Commented Sep 15, 2022 at 18:35
  • $\begingroup$ @ verret- Not yet. $\endgroup$ Commented Sep 15, 2022 at 18:54
  • $\begingroup$ @ Derek Holt - Many thanks. $\endgroup$ Commented Sep 15, 2022 at 18:55
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    $\begingroup$ @M.H.Hooshmand I think the expectation is that you've made some reasonable attempts to solve the question yourself before posting here... $\endgroup$
    – verret
    Commented Sep 15, 2022 at 18:57

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