awk - create a file based on another file -

i have text file contains following data. example, aa.txt has numbers. need extract continuous numbers(minimum 3 numbers) it.how can awk?

>aa.txt 31 35 36 37 38 39     44 169 170 173 174 175 177 206  >1a.txt 39 40 41 42 146 149 151 

my desired output shown below.

>aa.txt 35 36  37 38 39 173 174 175 >1a.txt  39  40  41  42 

using awk , example data:

awk 'f+1==$0 {a++} f+1!=$0 {if (a>1) {for (i=f-a;i<=f;i++) print i}a=0} {f=$0}' file 35 36 37 38 39 173 174 175 39 40 41 42 

some more readable:

awk ' f+1==$0 {     a++}  f+1!=$0 {     if (a>1) {         (i=f-a;i<=f;i++)             print         }a=0     }     {f=$0}     ' file 

how print file name:

awk 'fnr==1 {print ">"filename} f+1==$0 {a++} f+1!=$0 {if (a>1) {for (i=f-a;i<=f;i++) print i}a=0} {f=$0}' * 

change * match file criteria.