1, 6, f, 1c, 2d, 42, 5b, 78, 99 What is the first term of this hex sequence that is at least 9 digits and composed only of letters (a-f)?

hexpuzzle.py

#x = ['1', '6', 'f', '1c', '2d', '42', '5b', '78', '99']
#x = [ int(i,16) for i in x ]
#for i in x:
#    print hex(i)
#print x
#for i in range(1, len(x)):
#    print x[i]-x[i-1]

def lessthanf(x):    
    for i in x:
        if i.lower() > 'f':
            return False
    return True

offset = 33
current = 153
current_hex = ""

while True:
    offset += 4
    current += offset
   # print hex(current)
    current_hex = hex(current)[2:]
    if current_hex.isalpha() and len(current_hex) >= 9 and lessthanf(current_hex):
        print current_hex
        break