Here
it is claimed that every non-solvable number is divisible by $4$ and either $3$ or $5$. However, I did not find a number in the list not divisible by $3$.
So, my question :
Is there a non-solvable number NOT divisble by $3$ ?
Here
it is claimed that every non-solvable number is divisible by $4$ and either $3$ or $5$. However, I did not find a number in the list not divisible by $3$.
So, my question :
Is there a non-solvable number NOT divisble by $3$ ?
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The encyclopedia of integer sequences has a list of possible criteria for a number being a non-solvable number, nicely laid out here on MathOverflow. One of these is $2^{2p}(2^{2p}+1)(2^p-1)$, p odd prime.
The Suzuki groups are the only finite non-abelian simple groups with order not divisible by 3, and they have order $$2^{2(2n+1)}(2^{2(2n+1)} + 1)(2^{(2n+1)} −1)$$ which matches this criterion.
As mentioned by Derek Holt, it's also worth noting that since $2^{2(2n+1)}+1$ is divisible by $5$, it follows that all non-solvable groups whose order is not divisible by $3$ must be divisible by $5$.