%I
%S 0,10,25,28,29,32,41
%N Multiplicative persistence with squares of decimal digits: smallest number such that the number of iterations of "multiply digits squared" needed to reach 0 or 1 equals n.
%C This sequence is probably finite.
%C The number of times you need to multiply the square of the digits together before reaching 0 or 1 is equals to n.
%e a(4)= 29 > 4*81 = 324 > 9*4*16 = 576 > 25*49*36 = 44100 > 0 has persistence 4.
%t lst = {}; n = 0; Do[While[True, k = n; c = 0; While[k > 9, k = Times @@ IntegerDigits[k]^2; c++]; If[c == l, Break[]]; n++]; AppendTo[lst, n], {l, 0, 7}]; lst
%Y Cf. A003001, A031348, A031349.
%K nonn,hard,fini,base
%O 0,2
%A _Michel Lagneau_, May 22 2013
