This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A290328 #22 Jul 30 2017 03:53:43
%S A290328 0,0,4,0,3,0,3,1,1,0,7,0,2,2,20,0,19,0,5,2,19,0,4,1,1,52,1,0,51,0,1,2,
%T A290328 1,2,1,0,1,4,51,0,2,0,1,20,5,0
%N A290328 Iterate the map x -> A289667(x) starting at n; sequence gives number of steps to reach a prime, or -1 if no prime is ever reached.
%C A290328 Base 3 analog of A230626. See A290350 for the trajectory of 48.
%C A290328 If a(48) != -1, then a(48) > 120. - _Chai Wah Wu_, Jul 29 2017
%t A290328 Table[-1 + Length@ NestWhileList[FromDigits[#, 3] &@ Flatten@ Map[IntegerDigits[#, 3] &, FactorInteger[#] /. {p_, e_} /; p > 0 :> If[e == 1, p, {p, e}]] &, n, ! PrimeQ@ # &], {n, 2, 47}] (* _Michael De Vlieger_, Jul 29 2017 *)
%Y A290328 Cf. A289667, A230626, A195264, A290350, A290329.
%K A290328 nonn,more,base
%O A290328 2,3
%A A290328 _Chai Wah Wu_, Jul 27 2017