(l) means that the number must be converted in a letter based on its position in the alphabet 

>> http://pastebin.com/abcdefg

a(l [upper case])=1000 (binary)
b=9th fibonacci number
c(l)=22 (base 3)
d(l)=4th Catalan number
e(l [upper case])=x (x mod 2=1, x mod 5=3, x mod 7 = 2)
f=4th fibonacci number
g(l)=20