a couple of general formulas such as the the fangs

x = 25.10^k+1 y = 100(10^(k+1)+52)/25

give the vampire

v = xy = (10^(k+1)+52)10^(k+2)+100(10^k+1+52)/25 = x'.10^(k+2)+t
= 8(26+5.10^k)(1+25.10^k)

where x' denotes x with digits reversed