A070974 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Table of n, a(n) for n=1..52.

MATHEMATICA

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

PROG

(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, ", "); ); ))

CROSSREFS

Sequence in context: A302637 A230862 A281067 * A300022 A346783 A073619

Adjacent sequences: A070971 A070972 A070973 * A070975 A070976 A070977

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, May 17 2002

STATUS

approved