%I #8 Jan 17 2013 19:02:18

%S 0,1,8,10,20,20,41,44,86,66,147,210,175,264,255,259,426,425,362,387,

%T 500,489,447,449,389,559,419,517,633,444,529,534,795,950,826,813,1069,

%U 689,728,785,909,819,1013,1171,1218,996,1327,1330,891,1295,1342,1402

%N Number of steps to reach 1 in `3x+1' (or Collatz) problem starting with n!.

%t ns[n_]:=Length[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n!,#!=1&]]-1; Array[ ns,60] (* _Harvey P. Dale_, Jan 17 2013 *)

%o (PARI) for(n=2,100,s=n!; t=0; while(s!=1,t++; if(s%2==0,s=s/2,s=3*s+1); if(s==1,print1(t,","); ); ))

%K easy,nonn

%O 1,3

%A _Benoit Cloitre_, May 17 2002