3

is there a way to get binomial coefficients to appear inside a piecewise function? This is the code I am using right now:

$$ a(n,3)=% 

   \begin{cases}

     $ 1 {{k+2}\choose{2}} + 4 {{k+1}\choose{2}} + 1 {{k}\choose{2}}$ &\text{if $n\equiv0$ $\mod d$} \\
     $ 1 {{k+2}\choose{2}} + 5 {{k+1}\choose{2}} $ &\text{if $n\equiv1$ $\mod d$} \\
     $ 2 {{k+2}\choose{2}} + 4 {{k+1}\choose{2}} $ &\text{if $n\equiv d-1$ $\mod d$} \\
     $ 3 {{k+2}\choose{2}} + 3 {{k+1}\choose{2}} $ &\text{if $n\equiv d-1$ $\mod d$} \\
     $ 4 {{k+2}\choose{2}} + 2 {{k+1}\choose{2}} $ &\text{if $n\equiv d-1$ $\mod d$} \\
     $ 5 {{k+2}\choose{2}} + 1 {{k+1}\choose{2}} $ &\text{if $n\equiv d-1$ $\mod d$} \\
   \end{cases} $$

And This is the way that it is showing up. enter image description here

I need it to say

$1({k+2}\choose{2}) + 4 ({k+1}\choose{2})$,

and so on. I've tried putting extra brackets, but it still won't fix the formatting.

6

Welcome! You should no longer use $$ nor \choose. Also you should not add unnecessary $ signs. Here I think the dcases from mathtools makes sense.

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\[
a(n,3)=%
\begin{dcases}
  1 \binom{k+2}{2} + 4 \binom{k+1}{2} + 1 \binom{k}{2} &
    \text{if }n\equiv0 \mod d \\
  1 \binom{k+2}{2} + 5 \binom{k+1}{2}  &\text{if }n\equiv1 \mod d\\
  2 \binom{k+2}{2} + 4 \binom{k+1}{2}  &\text{if }n\equiv d-1 \mod d\\
  3 \binom{k+2}{2} + 3 \binom{k+1}{2}  &\text{if }n\equiv d-1 \mod d\\
  4 \binom{k+2}{2} + 2 \binom{k+1}{2}  &\text{if }n\equiv d-1 \mod d\\
  5 \binom{k+2}{2} + 1 \binom{k+1}{2}  &\text{if }n\equiv d-1 \mod d\\
\end{dcases} 
\]
\end{document}

enter image description here

| improve this answer | |
  • I hadn't changed the conditions on the side, because I was trying to figure out the binomial coefficients. – Lewis Apr 5 at 17:59
  • @lyne I see. That makes sense. – Schrödinger's cat Apr 5 at 18:00
  • Is it possible to get things to appear in this order: 1. The coefficients. 2. The conditions on the side. 3. A text underneath the function. 4. Binomial coefficients. – Lewis Apr 5 at 19:08
  • 2
    @lyne Would you mind asking a separate question on this where you add a sketch that clarifies what you are asking? (I am a bit lost because I do not understand the difference between "1. The coefficients" and "4. Binomial coefficients", and think that I did answer the original question. Asking questions is free of charge, and changing a question that has been answered is not optimal for others who have a similar problem.) – Schrödinger's cat Apr 5 at 19:14

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