Is this string a letter doing a cartwheel? Challenge inspiration was this that I saw somewhere:


  The word "nun" is just the letter n doing a cartwheel


Your challenge is to take a string and determine if it is the first letter doing a cartwheel.

Rules

A string is a letter doing a cartwheel if:


The first letter is the same as the last letter. (The letter can't land on its head.)
The string alternates between cartwheeling letters every one character.


The cartwheeling letters are n and u, m and w, b and q. Note that n and w together are not cartwheeling letters, and neither are w and b.


You will take a string using any of our standard input methods. 
You will output a truthy value if the string is a cartwheeling letter, and a falsy value if it is not. Output can be done using any standard output methods.


Additional rules:


Only lowercase cartwheel letters n/u/m/w/b/q need to be handled.
You may assume that input is never empty.
A one-character string is not a valid cartwheel.


Test cases

Input        -&gt; Output
nun          -&gt; truthy
nunun        -&gt; truthy
nunununu     -&gt; falsy
wmw          -&gt; truthy
wmwun        -&gt; falsy
bqbqbqbqbqb  -&gt; truthy
v^v^v        -&gt; falsy
AVAVA        -&gt; falsy
OOO          -&gt; falsy
ununununu    -&gt; truthy
nunwmwnun    -&gt; falsy
nun unun     -&gt; falsy
nunwmw       -&gt; falsy
nnuunnuunnuu -&gt; falsy
nwnwnwnwn    -&gt; falsy
m            -&gt; falsy
nunuuunun    -&gt; falsy


Winner

As with code-golf, the shortest code (in each language) wins!
sed 4.2.2, 30 + 1 -r = 43 31 bytes

Saved 12 bytes thanks to @Neil by shortening the first line

/nu|wm|qb/!d
/^((.).)\1*\2$/!d


Try it online!

Deletes input if falsey, otherwise does nothing to the input.

Explanation

With the -r flag, we do not need to use \( and \) for capturing groups and this saves bytes.

/nu|wm|qb/!                # On every line that does not match this regex
           d               # Delete
/^((.).)\1*\2$/!           # On every line that does not math
 ^((.).)                   #  the first two characters at the beginning of the line
        \1*                #  repeated
           \2$             #  with the first character at the end of the line
                d          # Delete