%I A031347
%S A031347 0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,2,4,6,8,0,2,4,6,8,0,3,6,9,
%T A031347 2,5,8,2,8,4,0,4,8,2,6,0,8,6,6,8,0,5,0,5,0,0,0,5,0,0,0,6,2,8,8,0,8,
%U A031347 8,6,0,0,7,4,2,6,5,8,8,0,8,0,8,6,8,6,0,6,0,8,4,0,9,8,4,8,0,0,8,4,8
%N A031347 Multiplicative digital root of n (keep multiplying digits of n until 
               reach a single digit).
%H A031347 T. D. Noe, <a href="b031347.txt">Table of n, a(n) for n=0..10000</a>
%H A031347 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               MultiplicativeDigitalRoot.html">Link to a section of The World of 
               Mathematics.</a>
%t A031347 mdr[n_] := NestWhile[Times @@ IntegerDigits@# &, n, UnsameQ, All]; Table[ 
               mdr[n], {n, 0, 104}] (from Robert G. Wilson v (rgwv(at)rgwv.com), 
               Aug 04 2006)
%o A031347 (PARI) A031347(n)= { local(resul); if(n<10, return(n) ); resul = n % 
               10; n = (n - n%10)/10; while( n > 0, resul *= n %10; n = (n - n%10)/
               10; ); return(A031347(resul)); } { for(n=1,80, print1(A031347(n),
               ","); ); } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 23 
               2006
%Y A031347 Cf. A007954, A010888, A007953, A031346, A003001.
%Y A031347 Sequence in context: A118943 A010879 A062078 this_sequence A087471 A128212 
               A007954
%Y A031347 Adjacent sequences: A031344 A031345 A031346 this_sequence A031348 A031349 
               A031350
%K A031347 nonn,base,easy,nice
%O A031347 0,3
%A A031347 Eric Weisstein (eric(AT)weisstein.com)