perl -nwe 'BEGIN{%u=qw(00 A 01 G 10 C 11 T);}$_=unpack("b32",pack("V",$_));s/00$//;while(/(..)/g){print $u{$1}}print"\n"' /afs/sipb/contrib/human-genome/stats/most-popular-15mers >! /afs/sipb/contrib/human-genome/stats/most-popular-15mers.txt 
AAAAAAAAAAAAAAA
ACACACACACACACA
AGTGCTGGGATTACA
CCTGTAATCCCAGCA
CCAGGCTGGAGTGCA
CCCAAAGTGCTGGGA
CCCAGCACTTTGGGA
ATATATATATATATA
AAAGTGCTGGGATTA
CACACACACACACAC
CTCTACTAAAAATAC
AAGTGCTGGGATTAC
GCCTGTAATCCCAGC
GCTGGGATTACAGGC
AGCACTTTGGGAGGC
CCAGCACTTTGGGAG
TGCTGGGATTACAGG
GGAGGCTGAGGCAGG
CAGCACTTTGGGAGG
TCCCAAAGTGCTGGG
TCCCAGCACTTTGGG
TGCACTCCAGCCTGG
ATCCCAGCACTTTGG
CCTCCCAAAGTGCTG
GTGTGTGTGTGTGTG
AATCCCAGCACTTTG
CTGAGGCAGGAGAAT
CCAAAGTGCTGGGAT
TATATATATATATAT
TGTAATCCCAGCACT
GCCTCCCAAAGTGCT
AGGCTGGAGTGCAGT
TGTGTGTGTGTGTGT
CAAAGTGCTGGGATT
GTAATCCCAGCACTT
TAATCCCAGCACTTT
TTTTTTTTTTTTTTT