OFFSET
1,25
COMMENTS
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).
Differs from A031346 first at n=110. [From R. J. Mathar, Sep 11 2008]
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1234)= 3 since f(1234)=13*24=312, f(312)=32*1=32 and
f(32)=3*2=6.
MAPLE
murthy:= proc(n) local L, d;
L:= convert(n, base, 10);
d:= nops(L);
add(L[2*i+1]*10^i, i=0..(d-1)/2)*add(L[2*i+2]*10^i, i=0..(d-2)/2)
end proc:
A087472:= proc(n) option remember;
if n < 10 then 0 else 1+procname(murthy(n)) fi
end proc:
map(A087472, [$1..200]); # Robert Israel, Feb 14 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Amarnath Murthy and Paul D. Hanna, Sep 11 2003
STATUS
approved