Laravel 5.4 - Validation with Regex

Below is my rule for project name:

$this->validate(request(), [
    'projectName' => 'required|regex:/(^([a-zA-z]+)(\d+)?$)/u',
];

I am trying to add the rule such that it must start with a letter from a-z or A-z and can end with numbers but most not.

Valid values for project name:

myproject123
myproject
MyProject

Invalid values for project name:

123myproject
!myproject
myproject 123
my project
my project123

I tried my regex online:

https://regex101.com/r/FylFY1/2

It should work, but I can pass the validation even with project 123.

via EdwardBlack