A 3- letter frequency
http://www.richkni.co.uk/php/crypta/freq.php
ata => 48
act => 31
taa => 30
agc => 29
tga => 28
aat => 27
cta => 26
ctg => 25
tag => 25
tat => 25
cgg => 23
gct => 22
tca => 22
cat => 21
aca => 21
gat => 19
aac => 19
cac => 18
ttt => 18
tac => 18
ccg => 17
gcc => 17
cgt => 17
gtc => 17
att => 17
caa => 16
tgt => 16
aaa => 16
tgc => 16
gac => 15
ttg => 15
ggc => 14
atc => 14
gta => 14
gca => 14
atg => 14
tcg => 13
aag => 12
gag => 12
gga => 12
gtt => 12
gtg => 12
gaa => 12
acg => 12
ggt => 12
aga => 11
ttc => 11
tta => 11
agt => 9
gcg => 9
cag => 9
agg => 9
tct => 9
cca => 8
ctt => 8
ctc => 8
cga => 7
acc => 7
tcc => 6
tgg => 6
ggg => 6
cct => 5
ccc => 5
cgc => 4
Frequency of letters in English:
e 12.702%
t 9.056%
a 8.167%
o 7.507%
i 6.966%
n 6.749%
s 6.327%
h 6.094%
r 5.987%
d 4.253%
l 4.025%
c 2.782%
u 2.758%
m 2.406%
w 2.360%
f 2.228%
g 2.015%
y 1.974%
p 1.929%
b 1.492%
v 0.978%
k 0.772%
j 0.153%
x 0.150%
q 0.095%
z 0.074%