function prettyprint(seq) -- approx DDBJ format
  seq = seq:gsub("%A",""):lower()
  local sums, n = { a=0, c=0, g=0, t=0 }, 1
  seq:gsub("(%a)", function(c) sums[c]=sums[c]+1 end)
  local function printf(s,...) io.write(s:format(...)) end
  printf("LOCUS       AB000000     %12d bp    mRNA    linear   HUM 01-JAN-2001\n", #seq)
  printf(" BASE COUNT %12d a %12d c %12d g %12d t\n", sums.a, sums.c, sums.g, sums.t)
  printf("ORIGIN\n")
  while n < #seq do
    local sub60 = seq:sub(n,n+59)
    printf("%9d %s\n", n, sub60:gsub("(..........)","%1 "))
    n = n + #sub60
  end
end

prettyprint[[
CGTAAAAAATTACAACGTCCTTTGGCTATCTCTTAAACTCCTGCTAAATG
CTCGTGCTTTCCAATTATGTAAGCGTTCCGAGACGGGGTGGTCGATTCTG
AGGACAAAGGTCAAGATGGAGCGCATCGAACGCAATAAGGATCATTTGAT
GGGACGTTTCGTCGACAAAGTCTTGTTTCGAGAGTAACGGCTACCGTCTT
CGATTCTGCTTATAACACTATGTTCTTATGAAATGGATGTTCTGAGTTGG
TCAGTCCCAATGTGCGGGGTTTCTTTTAGTACGTCGGGAGTGGTATTATA
TTTAATTTTTCTATATAGCGATCTGTATTTAAGCAATTCATTTAGGTTAT
CGCCGCGATGCTCGGTTCGGACCGCCAAGCATCTGGCTCCACTGCTAGTG
TCCTAAATTTGAATGGCAAACACAAATAAGATTTAGCAATTCGTGTAGAC
GACCGGGGACTTGCATGATGGGAGCAGCTTTGTTAAACTACGAACGTAAT
]]