OFFSET
1,1
COMMENTS
Inspired by A257491.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..70
EXAMPLE
The 1st divisor of 11 is 1, and the concatenation of 1 and 1 is 11.
The 2nd divisor of 25 is 5, and the concatenation of 2 and 5 is 25.
MATHEMATICA
Select[Range[10^5], (d = Divisors[n=#]; {} != Select[ Range@ Length@ d, FromDigits@ Flatten[ IntegerDigits /@{#, d[[#]]}] == n &, 1]) &] (* Giovanni Resta, Jun 08 2015 *)
PROG
(PARI) isok(n) = {d = divisors(n); for (k=1, #d, if (eval(concat(Str(k), Str(d[k]))) == n, return (1)); ); }
(Haskell)
a258738 n = a258738_list !! (n-1)
a258738_list = f [1..] where
f (x:xs) = if show x `elem` zipWith (++) kss (map show $ a027750_row' x)
then x : f xs else f xs
kss = map show [1..]
-- Reinhard Zumkeller, Jun 10 2015
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Michel Marcus, Jun 08 2015
STATUS
approved