How to make allowed values are 1 to 7, n and blank only?

function verify(frm) {
	if (frm.sc_scores.value > 7 || frm.sc_scores.value <= 0) {
		self.alert(frm.sc_scores.value + " is an invalid value! Allowed values are 1 to 7, n and blank");
		frm.sc_scores.focus();
	}
}

<input type="text" name="sc_scores" id="sc_scores" maxlength="1" size="2" value="<%= number %>" />

<input type="button" onClick="verify(this.form)" value="Edit" />

<script>

function verify(frm_field)
{

var allowed = /^[1-7n\s]{1}$/;

var field = document.getElementById(frm_field).value;

if (field.match(allowed)) {
  document.frm.onsubmit = function() {
   return true;
 }
}
else if (field.length == 0) {
  document.frm.onsubmit = function() {
   return true;
 }
}
else {
 alert(field + " is an invalid value! Allowed values are 1 to 7, n and blank");
}

}

</script>


<form name="frm" onsubmit="return false">
<input type="text" name="sc_scores" id="sc_scores" maxlength="1" size="2" value="<%= number %>"/>
<input type="submit" onClick="verify('sc_scores')" value="Edit" />
</form>