A travesty of upvoting

The most upvoted solution, which has 13 upvotes, is nice, short, and intuitive, but not rigorous. The best rigorous solution has 3 upvotes while mine, which is more complete has 1.

Not really whining, but something seems wrong with the upvote system.

EDIT: He said: 2^1 ends in 2 2^2 ends in 4 2^3 ends in 8 2^4 ends in 6 2^5 ends in 2 2^4k ends in 6.

Why does 2^4k end in 6? It is not explained at all.

• Welcome to SE! This is how it works. :-)
– quid Mod
Dec 14 '14 at 2:12
• I don't think Fermat's Little Theorem is required to tell that $2^4$ is congruent to $1$ modulo $5$, or that $6 \times 6 = 36$ which also ends in $6$. There is rigor, and then there is unneeded rigor... Dec 14 '14 at 2:16
• I didn't vote on that question, but if I had I would have voted for that answer. That answer computed until there was a repeat. This is the basis for a simple yet completely rigorous way to do it. These sorts of problems can be explained to grade school kids. (But yes, in general, voting can be arbitrary; that is its nature.)
– aes
Dec 14 '14 at 2:51
• The upvote button says "This answer is useful" not "This answer is rigorous". Dec 14 '14 at 3:22
An aside: with a username that contains the term "troll," you may find that people aren't too sympathetic when you complain. :)