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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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Inspired by A228276.
LINKS
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
Sequence in context: A153273 A276486 A341363 * A332701 A342158 A344544
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

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Last modified May 20 02:14 EDT 2024. Contains 372703 sequences. (Running on oeis4.)