

A234932


The product a(n)*a(n+1) can be written using the digits of {a(n),a(n+1)}; always choose the smallest possible unused positive integer.


4



1, 2, 10, 3, 51, 30, 100, 4, 16, 40, 160, 352, 151, 34, 106, 25, 13, 24, 26, 240, 130, 250, 133, 295, 313, 1000, 5, 19, 50, 102, 6, 21, 60, 127, 171, 241, 175, 109, 45, 181, 450, 187, 400, 166, 3052, 1196, 302, 2865, 1441, 298, 31, 1165, 139, 7, 1015, 70, 1043, 700, 1168, 412, 1702, 125
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OFFSET

1,2


COMMENTS



LINKS

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 !! (n1)
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


CROSSREFS



KEYWORD

nonn,base,nice


AUTHOR



EXTENSIONS



STATUS

approved



