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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 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 Cf. A228276 Sequence in context: A153273 A276486 A341363 * A332701 A342158 A344544 Adjacent sequences: A234929 A234930 A234931 * A234933 A234934 A234935 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.)