primes :: [Int]
primes = mapMaybe log2 $ fractran prog 2
where
prog =
[ 17 % 91
, 78 % 85
, 19 % 51
, 23 % 38
, 29 % 33
, 77 % 29
, 95 % 23
, 77 % 19
, 1 % 17
, 11 % 13
, 13 % 11
, 15 % 14
, 15 % 2
, 55 % 1
]
log2 = fmap succ . elemIndex 2 . takeWhile even . iterate (`div` 2)