%I #15 Sep 08 2022 08:44:50
%S 0,4,3,3,3,3,2,2,3,1,1,4,3,3,3,3,2,2,3,1,4,3,3,2,2,2,3,3,2,1,3,3,3,2,
%T 2,2,3,3,3,1,3,2,2,3,2,3,3,2,3,1,3,2,2,2,2,2,2,2,2,1,3,2,2,3,2,3,3,2,
%U 2,1,2,3,3,3,2,3,2,3,3,1,2,3,3,2,2,2,3,3,3,1,3,2,3,3,2,2,3,3,2
%N 4-multiplicative persistence: number of iterations of "multiply 4th powers of digits" needed to reach 0 or 1.
%H Seiichi Manyama, <a href="/A031350/b031350.txt">Table of n, a(n) for n = 1..10000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/MultiplicativePersistence.html">Multiplicative Persistence</a>
%o (Magma) pers:=func<n,e|&*[c^e:c in Intseq(n)]>; a:=[0]; for n in [2..100] do m:=1; k:=n; while not pers(k,4) in {0,1} do k:=pers(k,4); m:=m+1; end while; Append(~a,m); end for; a; // _Marius A. Burtea_, Jan 13 2020
%K nonn,base
%O 1,2
%A _Eric W. Weisstein_
%E Offset 1 from _Seiichi Manyama_, Jan 13 2020