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Sep 26, 2021 at 13:39 vote accept T. Amdeberhan
Sep 25, 2021 at 18:41 history edited Max Alekseyev CC BY-SA 4.0
some lead
Sep 25, 2021 at 18:32 history edited Max Alekseyev CC BY-SA 4.0
more accurate
Sep 25, 2021 at 17:06 history edited Max Alekseyev CC BY-SA 4.0
added 386 characters in body
Sep 25, 2021 at 11:32 comment added Max Alekseyev For an odd $m$, we have $2\sigma(m)\equiv 2\tau(m)\pmod4$.
Sep 25, 2021 at 5:13 comment added მამუკა ჯიბლაძე Sorry, one more question: in the last display, should not it be $\sigma$ rather than $\tau$?
Sep 24, 2021 at 18:14 comment added მამუკა ჯიბლაძე @GHfromMO Max I see, thanks
Sep 24, 2021 at 16:57 history edited Max Alekseyev CC BY-SA 4.0
added some lead ; added 7 characters in body
Sep 24, 2021 at 16:48 comment added Max Alekseyev @მამუკაჯიბლაძე: Perhaps, the easiest way is to think of the coefficient 4 as $x$ satisfying $x^2\equiv 0$. Then $$\prod_i (1+xc_i) \equiv 1 + x\sum_i c_i.$$
Sep 24, 2021 at 16:18 comment added GH from MO მამუკა ჯიბლაძე: $4$ times $4$ is divisible by $8$. Of course the congruence is meant in the ring $\mathbb{Z}[[q]]$.
Sep 24, 2021 at 16:06 comment added მამუკა ჯიბლაძე How do you pass from the first congruence to the second?
Sep 24, 2021 at 16:03 history edited Max Alekseyev CC BY-SA 4.0
added 12 characters in body
Sep 24, 2021 at 15:26 history answered Max Alekseyev CC BY-SA 4.0