Happy new year 2021

Question

Happy new year to all mathematics lover. I am looking for some mathematical way to say Happy new year 2021. If possible, then please show your ideas.

$$\color{red}{\binom {20}{19}} +\color{orange}{\binom {19}{16} +{\binom {16}{14}}}+ \color{green}{\binom {14}{12} +\binom {12}{7}}+ \color{blue}{\binom {7}{6}+ \binom {6}{5}}+ \color{purple}{\binom {5}{3}+\binom {3}{1}}+ \color{magenta}{\binom {2}{0}}+\color{magenta}{\binom {1}{1}}+\color{magenta}{\binom {1}{0}} =\color{red}{2021}$$

Above idea is copied from here.

Mathematical way of saying "2021" or "Happy new year 2021"? Either way, same to you, but your question is going to be closed for lacking focus (too broad) unless you do something about it. — Sarvesh Ravichandran Iyer, Jan 01 '21 at 04:59
Math contests like ARML typically have problems that have combinatoric properties of either the current or next year. So that should provide ideas by looking at years past. For example, 2016 being the largest triangular number of the form $(q^2-1)(q^2-q)$ — AHusain, Jan 01 '21 at 05:07
@TeresaLisbon Best wishes...and thanks I updated my question. — Unknown, Jan 01 '21 at 05:10
@AmanPandey Just saw it, best wishes and +1. (Is it $\binom 21$ instead of $\binom 20$ at the end?) — Sarvesh Ravichandran Iyer, Jan 01 '21 at 05:10
@TeresaLisbon I copied it from a link there is for 2019. I just add two combinations to get two. — Unknown, Jan 01 '21 at 05:13
This is not a question, but just a commemoration for the new year, which is not appropriate to be a question. — Hanul Jeon, Jan 01 '21 at 05:47
@TeresaLisbon https://math.stackexchange.com/q/4144258/469000 — Unknown, May 19 '21 at 14:30
I have added the tag [recreational-mathematics] - just to recall that this tag is available and that possibly then also questions that match this tag are possible... The needed focus will be maybe available at the end of December 2021 or beginning of January 2022. — dan_fulea, Oct 18 '21 at 12:24

score 3 · Answer 1 · answered Jan 01 '21 at 05:06

3

A product of two consecutive primes is a four digit number $N$, written as (the string concatenation of) two consecutive natural numbers. Well, $N$ is...

answered Jan 01 '21 at 05:06

dan_fulea

32,856

1

The downvoter of this answer may also share my opinion that this is rather a joke than a mathematical issue. Yes, nobody "concatenates" two natural numbers, this is not a part of mathematics. And of course, two mathematicians (on this site) never consider such an issue to say "Happy new year 2021!", since "Happy new year 2021!" is not a mathematical issue. But in this comment, it is allowed to do it, so for all mathematicians and non-mathematicians: "Happy new year 2021!" :: Both elliptic curves $\color{blue}{y^2 = x^3+2021x}$ and $\color{blue}{y^2=x^3 +2021}$ have rank one! – dan_fulea Jan 01 '21 at 06:18
This is really nice! – Unknown Jan 01 '21 at 10:34
Somebody insisted to downvote again... OK, so i have added the tag [recreational-mathematics] - just to show that this tag is available and that possibly then also questions that match this tag are possible... Please give a reason for the downvotes so that i can correct the answer to match the complains... – dan_fulea Oct 18 '21 at 12:25

Happy new year 2021

1 Answers1