OFFSET
1,1
COMMENTS
This is not a duplicate of A129800, which accepts "07" for example as the second prime.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..5000
EXAMPLE
113 is in the sequence because 11 and 3 are both primes, but 1 and 13 are not both primes, so there is one way.
MATHEMATICA
spl[n_] := Block[{d = IntegerDigits@n, c = 0, z}, z = Length@d; Do[If[PrimeQ@ FromDigits@ Take[d, k] && d[[k + 1]] > 0 && PrimeQ@ FromDigits@ Take[d, k - z], c++], {k, z - 1}]; c]; Select[ Prime@ Range@ 300, spl[#] == 1 &] (* Giovanni Resta, Feb 27 2014 *)
PROG
(Haskell)
a238056 n = a238056_list !! (n-1)
a238056_list = filter ((== 1) . length . f) a000040_list where
f x = filter (\(us, vs) ->
head vs /= '0' &&
a010051' (read us :: Integer) == 1 &&
a010051' (read vs :: Integer) == 1) $
map (flip splitAt $ show x) [1 .. length (show x) - 1]
-- Reinhard Zumkeller, Feb 27 2014
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Colin Barker, Feb 17 2014
STATUS
approved