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A045777 a(1)=1, a(2)=2; thereafter successive products of pairs of digits make further digits. 2

%I

%S 1,2,2,4,8,3,2,2,4,6,4,8,2,4,2,4,3,2,1,6,8,8,8,1,2,6,2,6,4,8,6,4,6,4,

%T 8,2,1,2,1,2,1,2,2,4,3,2,4,8,2,4,2,4,2,4,3,2,1,6,2,2,2,2,2,2,4,8,1,2,

%U 6,8,3,2,1,6,8,8,8,8,8,1,2,6,2,6,1,2,4,4,4,4,4,8,3,2,8,2,1,2,4,8,2,4,6,2,6

%N a(1)=1, a(2)=2; thereafter successive products of pairs of digits make further digits.

%C The numbers 0, 5, 7, and 9 never appear, but arbitrarily long sequences of 8's appear.

%D Erich Friedman, Puzzles of the Week, https://erich-friedman.github.io/mathpuzzle/

%H T. D. Noe, <a href="/A045777/b045777.txt">Table of n, a(n) for n = 1..15212</a>

%e 1*2=2 2*2=4 2*4=8 4*8=32 8*3=24...

%t t = {1, 2}; Do[ t = Join[t, IntegerDigits[t[[n-1]] t[[n-2]]]], {n, 3, 100}]; t

%K easy,nonn,base

%O 1,2

%A _Erich Friedman_

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Last modified September 26 06:16 EDT 2021. Contains 347664 sequences. (Running on oeis4.)