A070974 Number of steps to reach 1 in `3x+1' (or Collatz) problem starting with n!.

0, 1, 8, 10, 20, 20, 41, 44, 86, 66, 147, 210, 175, 264, 255, 259, 426, 425, 362, 387, 500, 489, 447, 449, 389, 559, 419, 517, 633, 444, 529, 534, 795, 950, 826, 813, 1069, 689, 728, 785, 909, 819, 1013, 1171, 1218, 996, 1327, 1330, 891, 1295, 1342, 1402

Offset: 1

Author

Benoit Cloitre, May 17 2002

Keywords

• easy
• nonn

Programs

Mathematica

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

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,","); ); ))