OFFSET
1,2
COMMENTS
Inspired by A228276.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
E. Angelini, Add A to B
E. Angelini, Add A to B [Cached copy, with permission]
EXAMPLE
1*2 = 2 uses only digits from {1,2},
2*10 = 20 uses only digits from {2,1,0},
10*3 = 30 uses only digits from {1,0,3}.
What comes after 3? Call it x. 3*x must use only digits from 3 and the digits of x. Surprisingly x=51 is the first (unused) number which works.
And so on.
PROG
(Haskell)
import Data.List ((\\), delete)
a234932 n = a234932_list !! (n-1)
a234932_list = 1 : f 1 [2..] where
f x zs = g zs where
g (y:ys) = if null $ show (x * y) \\ (show x ++ show y)
then y : f y (delete y zs) else g ys
-- Reinhard Zumkeller, Jul 26 2014
CROSSREFS
KEYWORD
nonn,base,nice
AUTHOR
Claudio Meller, Jan 01 2014
EXTENSIONS
Entered by N. J. A. Sloane on Claudio Meller's behalf and submitted for the 2014 JMM competition with his permission.
STATUS
approved