In the given sequence, the number of letters preceded by a symbol and followed by a number is ______ .
$M@A#N2B4O&3C5P+D21
1
2
4
3
3
4
2
In the given sequence, the number of letters preceded by a symbol and followed by a number is ______ .
$M@A#N2B4O&3C5P+D2