Is case sensitivity important?
JavaScript (ES7), 43 bytes



f=(n,a=53,b=27)=&gt;n?--n?f(n,a*63,b*37):a-b:0
&lt;input type=number value=0 min=0 max=9 style=width:4ch oninput=o.textContent=f(+this.value)&gt;&lt;div id=o&gt;0&lt;/div&gt;




Not reduces day today - 55 bytes.