%I A087472
%S A087472 0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,1,1,1,1,2,2,
%T A087472 2,2,2,3,1,1,1,2,2,2,2,3,2,3,1,1,2,2,2,3,2,3,2,3,1,1,2,2,2,2,3,2,3,3,1,
%U A087472 1,2,2,3,3,2,4,3,3,1,1,2,2,2,2,3,3,3,3,1,1,2,3,3,3,3,3,3,2,1,1,1,1,1,1
%N A087472 Number of iterations required for the function f(n) to reach a single 
               digit, where f(n) is the product of the two numbers formed from the 
               alternating digits of n.
%C A087472 A087471(n) gives the final digit reached by successive iterations of 
               Murthy's function, f(n). A087473(n) gives the smallest number that 
               requires n iterations of Murthy's function to reach a single digit. 
               The n-th row of triangle A087474 gives the n successive iterations 
               of Murthy's function on A087473(n).
%C A087472 Differs from A031346 first at n=110. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Sep 11 2008]
%e A087472 a(1234)= 3 since f(1234)=13*24=312, f(312)=32*1=32 and
%e A087472 f(32)=3*2=6.
%Y A087472 Cf. A087471, A087473, A087474.
%Y A087472 Sequence in context: A102675 A143544 A031346 this_sequence A054348 A037813 
               A159700
%Y A087472 Adjacent sequences: A087469 A087470 A087471 this_sequence A087473 A087474 
               A087475
%K A087472 nonn,base
%O A087472 1,25
%A A087472 Amarnath Murthy (amarnath_murthy(AT)yahoo.com) and Paul D. Hanna (pauldhanna(AT)juno.com), 
               Sep 11 2003